JOHNSTONE CENTRE
RESEARCH IN NATURAL RESOURCES & SOCIETY
Environmental Consulting
Report No. 27
Ecological Assessment of Cyclic Release Patterns (CRP)
from Dartmouth Dam to the Mitta Mitta River, Victoria.
MDBC
Lachlan Sutherland
Darren Ryder
Robyn Watts
___________
August 2002
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
EXECUTIVE SUMMARY
Background
• The Johnstone Centre Environmental Consulting team were contracted to
undertake an ecological assessment of the CRP from Dartmouth Dam to the Mitta
Mitta River between December 2001 and February 2002.
• Four sites in the Mitta Mitta River and one reference site in the unregulated
tributary of Snowy Creek were sampled during this study. Extensive cobble banks
were present at all sites. Two cobble habitats were sampled during the study:
permanently inundated cobble that was inundated throughout the project and
newly inundated cobble that was inundated only during periods of high flow.
• Nine sampling events took place during the project, one on the final day of the
first variable flow release, three during each of the second and third variable flow
releases and two during the subsequent low and constant flow period.
• The following indicators were assessed:
Water Quality
Dissolved organic carbon (DOC)
Particulate organic matter (POM)
Total suspended solids (TSS)
Water column chlorophyll-a (Chl-a)
Temperature, conductivity, dissolved oxygen, pH
River Productivity
Biofilm Composition
Benthic production/respiration
Water column production
Bacterial activity of the water column
Macroinvertebrates
Benthic invertebrates in cobble and littoral habitats
Effects of CRP
•
The cyclic release pattern from Dartmouth Dam to the Mitta Mitta River led to
substantial changes in the water quality and biotic parameters measured in this
study. In contrast, over the same period of time there was generally no change in
these parameters measured at the reference site in Snowy Creek.
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
•
The water quality in the Mitta Mitta River during the CRP differed from that
during the 37 days of constant low flows that followed the releases. There was
lower conductivity, pH, temperature, and higher POM, TSS and Chl-a in the Mitta
Mitta River during the CRP than in the constant low flow period.
•
There was scouring of biofilms during each peak flow of the CRP in the Mitta
Mitta River resulting in slight decreases in the biomass of biofilms, increased
activity of some dominant classes of enzymes in the water column, changed
composition of biofilm algal species and rapid changes in net productivity at all
four sites in the Mitta Mitta River.
•
The response of macroinvertebrates to the CRP was more pronounced at site one
(the most upstream site) than at the other sites. There was an increased number of
families and increased SIGNAL scores observed only at site one, however there
were significant changes in the community composition of macroinvertebrates at
three of the four sites in the Mitta Mitta River.
Effects of 37 days of constant low flows following the CRP
•
Many water quality and biotic parameters displayed substantial changes during the
37 days of low and constant flows that followed the CRP in the Mitta Mitta River.
In contrast, over the same period there was no change in most of the parameters
measured at the reference site in Snowy Creek.
•
Biofilm biomass increased during the constant flow period in the Mitta Mitta
River. This coincided with very low activity of enzymes in the water column,
altered composition of biofilm algal species to dominance of fewer, late
successional taxon and decreased net productivity.
•
The response of macroinvertebrates during the constant flows differed between
sites. At site one there was no change in the number of families but the SIGNAL
score increased, suggesting that the ecological effects of the CRP at this site were
still being realised. In contrast, there was an increased abundance of tolerant
families and decreased abundance of more sensitive families at sites two and three
by the end of the constant flow period.
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
ACKNOWLEDGMENTS
Many people have been involved in this project, mainly in the field and laboratory
components. Martin Asmus, Daniel Francis, Bruce Mullins, Dr Darren Ryder, Angus
Sutherland and Lachlan Sutherland all took part in sampling of the Mitta Mitta River
and Snowy Creek over the study period. Numerous people including, Nigel Anthony,
Michelle Burton, Toby Edmunds, Dr Darren Ryder, Claire Sims, Angus Sutherland,
Lachlan Sutherland and Dr Robyn Watts assisted in processing the samples that were
collected during the project. Special thanks must also go to Dr Adrienne Burns and
Andrea Wilson for identifying micro flora and fauna samples, respectively. Special
thanks to Lyn and Ted at the Mitta Mitta Caravan Park, and Steven Lord of Bowler
Station who allowed access through his property.
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CONTENTS
EXECUTIVE SUMMARY ..................................................................................................... 2
ACKNOWLEDGMENTS....................................................................................................... 4
1.0 INTRODUCTION .......................................................................................................... 7
1.1 TERMS OF REFERENCE .................................................................................................. 7
1.2 MANAGEMENT EXPECTATIONS - INTENT OF THE PROGRAM ........................................ 7
1.3 BACKGROUND PROJECT INFORMATION........................................................................ 8
1.3.1 Cyclic Release Pattern......................................................................................... 8
1.3.2 Recommended Environmental Indicators ............................................................ 9
2.0 PROJECT DESIGN ..................................................................................................... 10
2.1 PROJECT OBJECTIVES ................................................................................................. 10
2.2 ENVIRONMENTAL INDICATORS .................................................................................. 10
2.2.1 Additional Parameters....................................................................................... 12
2.3 STUDY AREA .............................................................................................................. 13
2.3.1 Hydrographic Data of the Mitta Mitta River and Snowy Creek ........................ 14
2.3.2 Sites Locations and Descriptions....................................................................... 15
2.4 PROJECT DESIGN ........................................................................................................ 17
2.4.1 Temporal Comparisons ..................................................................................... 18
2.4.2 Longitudinal Comparisons ................................................................................ 18
2.4.3 Reference Stream ............................................................................................... 18
2.4.4 Relevance of Reference Site............................................................................... 19
2.5 SAMPLING REGIME ..................................................................................................... 20
2.5.1 Project Limitations ............................................................................................ 20
2.6 PREDICTIONS .............................................................................................................. 21
2.6.1 Water Quality..................................................................................................... 21
2.6.2 Enzyme activity .................................................................................................. 21
2.6.3 Biofilm composition ........................................................................................... 22
2.6.4 Benthic Metabolism ........................................................................................... 22
2.6.5 Macroinvertebrates............................................................................................ 23
3.0 HYDROGRAPHIC DATA DURING STUDY PERIOD .......................................... 24
4.0 WATER QUALITY...................................................................................................... 26
4.1 INTRODUCTION ........................................................................................................... 26
4.2 METHODS ................................................................................................................... 27
4.2.1 Field Methods .................................................................................................... 27
4.2.2 Laboratory Methods .......................................................................................... 28
4.2.3 Data Manipulation and Analysis ....................................................................... 29
4.3 RESULTS ..................................................................................................................... 29
4.3.1 POM, DOC, TSS and Chl-a ............................................................................... 29
Yeokal Multiprobes ......................................................................................................... 35
4.3.3 Water Column Nutrient...................................................................................... 36
4.3.4 DOC and POM Loading.................................................................................... 36
4.4 DISCUSSION ................................................................................................................ 38
4.4.1 Water Quality Parameters ................................................................................. 38
4.4.2 DOC and POM Loading.................................................................................... 41
4.5 SUMMARY OF FINDINGS ............................................................................................. 41
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
5.0 WATER COLUMN EXTRACELLULAR ENZYME ACTIVITY.......................... 43
5.1 INTRODUCTION ........................................................................................................... 43
5.2 METHODS ................................................................................................................... 44
5.2.1 Field methods..................................................................................................... 44
5.2.2 Laboratory Methods .......................................................................................... 44
5.2.3 Data Manipulation and Analysis ....................................................................... 45
5.3 RESULTS ..................................................................................................................... 45
5.4 DISCUSSION ................................................................................................................ 49
5.5 SUMMARY OF FINDINGS .............................................................................................. 51
6.0 BIOFILM STRUCTURE AND FUNCTION ............................................................. 52
6.1 INTRODUCTION ........................................................................................................... 52
6.2 METHODS ................................................................................................................... 54
6.2.1 Biofilm Structural Components ......................................................................... 54
6.2.2 Biofilm Taxonomy.............................................................................................. 55
6.2.3 Biofilm metabolism ............................................................................................ 55
6.2.4 Data Manipulation and Analysis ....................................................................... 57
6.3 RESULTS ..................................................................................................................... 58
6.3.1 Biofilm total, organic and algal biomass........................................................... 58
6.3.2 Biofilm Algal Species Composition.................................................................... 69
6.3.3 Biofilm metabolism ............................................................................................ 76
6.4 DISCUSSION. ............................................................................................................... 78
6.5 SUMMARY OF FINDINGS ............................................................................................. 82
7.0 MACROINVERTEBRATES....................................................................................... 84
7.1 INTRODUCTION ........................................................................................................... 84
7.2 METHODS ................................................................................................................... 85
7.2.1 Field methods-Cobble habitats.......................................................................... 85
7.2.2 Field methods-Littoral habitats ......................................................................... 86
7.2.3 Laboratory methods........................................................................................... 86
7.2.4 Data Manipulation and Analyses ...................................................................... 86
7.3 RESULTS ..................................................................................................................... 87
7.3.1 Overview of macroinvertebrate data ................................................................. 87
7.4 DISCUSSION .............................................................................................................. 103
7.5 SUMMARY OF FINDINGS ............................................................................................ 105
8.0 SUMMARY & RECOMMENDATIONS ................................................................. 107
8.1 EFFECTS OF VARIABLE FLOW RELEASES ON THE ECOLOGICAL CONDITION OF THE
MITTA MITTA RIVER ......................................................................................................... 107
8.2 EFFECTS OF 37 DAYS CONSTANT AND LOW FLOWS ON THE ECOLOGICAL CONDITION OF
THE MITTA MITTA RIVER.................................................................................................. 109
8.3 RECOMMENDATIONS FOR FUTURE MONITORING PROGRAMS ................................... 111
9.0 REFERENCES ........................................................................................................... 114
APPENDIX 1 - PROJECT BREIF .................................................................................... 120
APPENDIX 2 - JOHNSTONE CENTRE PROPOSAL ................................................... 130
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
1.0 INTRODUCTION
1.1
Terms of Reference
The Johnstone Centre – Environmental Consulting (JC) team were contracted by the
Murray Darling Basin Commission (MDBC) to undertake an ecological assessment of
a cyclic release pattern (CRP) in the Mitta Mitta River, Victoria between December
2001 and February 2002. The Terms of Reference offered to JC were in the form of
four documents (Appendix 1): requirements for tenders (Tony McCleod, November
2001), summary of the proposed variable release pattern (David Dole, August 2001;
John Riddiford, November 2001) and the ecosystem components to be assessed
(Terry Hillman, November 2001).
The JC proposal (Appendix 2), with the inclusion of various amendments (Robyn
Watts, November 2001) was used as the Terms of Reference for the project.
1.2
Management Expectations - Intent of the Program
Flow conditions within the Mitta Mitta River are highly regulated by Dartmouth Dam.
The timing and duration of releases from Dartmouth are dependent upon the status of
the other major water storages in the River Murray system, particularly Hume
Reservoir. Dartmouth plays an important role as a relatively secure ‘drought reserve
storage’.
In wet years, little or no transfers are required from Dartmouth Dam unless a spill
event occurs. However, in dry years, it can be necessary to transfer large volumes
from Dartmouth as reserves are depleted in downstream water storages. The risk that
transfers from Dartmouth may result in a spill from Hume during wet climatic
conditions, transfers are often delayed until later in the season. An exception to this
(which occurred in the 2001/2002 season) occurs when Dartmouth nears capacity
(≥80%) and ‘harmony transfers’ are required. These are made when the probability of
Dartmouth spilling exceeds Hume, and that for at which time transfers are made to
equalise the probability of spill from each storage.
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
River Murray Water’s (RMW) management of harmony transfers attempts to
minimise floodplain inundation and, maintain relatively constant discharge levels. The
River Murray Expert Panel for Environmental Flows (RMEPEF) highlighted constant
flow conditions as having detrimental impacts upon the instream and floodplain
environments of the Murray River Catchment.
Following the outcomes of discussions by the RMEPEF, RMW proposed the
introduction of a CRP to their harmony transfers from Dartmouth Dam to the Mitta
Mitta River in the 2001/02 season. The CRP comprises of repeated flow releases that
attempt to mimic minor natural flood events and are consistent with the
recommendations of the Expert Panel (Table 1.1).
The intent of the CRP was to introduce flow variability to their transfers from
Dartmouth Dam to Hume Weir, for the ecological benefit of the Mitta Mitta River. As
part of the introduction of the CRP the MDBC sought assistance in assessing the
ecological effects of this modification to management practice and intended that the
work would aim to:
•
Identify components of the ecosystem which might be expected to respond to a
change from constant to variable flow patterns on the proposed scale;
•
Provide measurements indicative of that response;
•
Form the basis for preliminary assessment and advice for management of variable
releases, and;
•
Provide data and insights, which could support and help direct more rigorous
studies in the future.
1.3
Background Project Information
1.3.1 Cyclic Release Pattern
River Murray Water presented the following CRP proposal to the Mitta Mitta Water
Services Committee on the 14/11/2001. The JC project was designed to assess the
ecosystem response to the proposed pattern (Table 1.1). The proposed CRP comprised
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
three identical variable flow releases. Detailed summary of the proposed CRP is
contained in Appendix 1 (David Dole, August 2001).
Table 1.1: Summary of the variable flow releases from Dartmouth Dam during the cyclic
release pattern (CRP) for the Mitta Mitta River between 19/11/2001 and 31/12/2001.
Prepared by River Murray Water, 14/11/2001.
Cyclic Release Pattern
Number of variable flow releases
Duration of each release
Flow Rise
Flow Recession
First pulse proposed to commence
Colemans Gauge
Average flow required
Maximum Flow
Minimum Flow
Average Water Level (Colemans gauge)
Water Level Variation
Tallandoon Gauge *
Average flow
Maximum Flow
Minimum Flow
Average Water Level (Tallandoon gauge)
Water Level Variation
3
14 days
2 days
12 days
Week commencing 19/11/01
4000 ML/day
4800 ML/day
3200 ML/day
2.08 m
0.25 m total
5000 ML/day
5800 ML/day
4200 ML/day
2.43 m
0.25 m total
1.3.2 Recommended Environmental Indicators
A suite of environmental indicators were identified for assessment by Dr Terry
Hillman, 14/11/2001 (Appendix 1). The assessment of these parameters was intended
to provide an indication of ecosystem response to the CRP. The environmental
indicators recommended for assessment included water quality parameters, river
productivity parameters (eg. biofilm composition, benthic production / respiration,
water
column
production,
enzyme
activity),
invertebrates
(benthic
macroinvertebrates) and the activity of fish larvae.
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
2.0 PROJECT DESIGN
2.1
Project Objectives
The main objective of the project was to record the response of selected
environmental indicators to the CRP from Dartmouth Dam to the Mitta Mitta River,
Victoria. The study was conducted between December 2001 and February 2002 and
comprised field and laboratory experiments for four sites on the Mitta Mitta River and
one site on Snowy Creek. Environmental indicators assessed in this project covered
pelagic and benthic cobble bench habitats. The response of environmental indicators
was used to make an assessment of ecological effects of the modifications to harmony
transfer management practice and provide recommendations for future manipulation
of transfers for environmental benefit.
The specific project objectives stated in a Draft Study Brief (Hillman, 14/11/2001)
provided in the tender documents were that the JC research team would:
•
Identify components of the ecosystem which might be expected to respond to a
change from constant to variable flow patterns on the proposed scale;
•
Provide measurements indicative of that response;
•
Form the basis for preliminary assessment and advice for management of variable
releases, and;
•
Provide data and insights, which could support and help direct more rigorous
studies in the future.
2.2
Environmental Indicators
Assessing the ecological 'health' of river systems is an important issue for ensuring
both the long term ecological condition of the river system and the sustainability of
development dependant on the water resource. Indicators form the basis of most
empirical systems for assessing the status of the environment (Fairweather 1999).
Environmental indicators are measures of physical, chemical or biological responses
to environmental change.
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
In selecting environmental indicators for the assessment of ecological change, there is
a need to identify the stressors on the system and identify which components and
processes are likely to be affected (Cairns et al. 1993). The selection of environmental
indicators must therefore depend in part on the projected outcomes of the proposed
management regime. Fairweather (1999) postulates three approaches to selecting
specific indicators; (1) a haphazard selection from divergent perspectives (2) a single
perspective based on previous data, and (3) a synthetic approach that integrates
distinct perspectives.
The project team identified the loss of flow variability to be the major stressor on the
pelagic environment of the Mitta Mitta River. Based on previous research conducted
within the Murrumbidgee River Catchment (Watts et al. 2000) the team identified that
benthic biofilm composition and production, enzyme activity and the structure of
benthic macroinvertebrate assemblages would be the instream components most likely
affected by the lack of flow variability. These components have also been
demontrated to respond rapidly to changes in flow conditions. The selection of
environmental indicators was based on previous data and research. The indicators
selected were:
•
Extracellular enzyme activity of water column bacteria, included five
methylumbelliferyl (MUF) labelled carbon substrates that were used to estimate
bacterial activity in water samples (1) 4-MUF-butyrate (fatty acid esterase –
FAE); (2) α-D-glucosidase (carbohydrate), (3) β-D-glucosidase (carbohydrate);
(4) β-D-xylosidase (long chain carbohydrate, eg. woody substrates), and (5)
Leucine-7-amino-4-methyl-coumarin (aminopeptidase). These enzymes are
involved in the degradation of polysaccharides, carbohydrates and proteins
derived from a range of authochthonous and allocthonous organic matter (Chrost
1991);
•
Biofilm structure and function, includes assessment of biofilm composition and
metabolism. Selected because changes to the species composition and metabolic
rate of algal biofilms can impact on their ecosystem function, by either reducing
or increasing oxygen production dependant on species present and controlling
food resources for primary consumers;
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
•
Macroinvertebrate composition, included assessments of benthic and littoral
habitats. Macroinvertebrates are used in biological monitoring programs
worldwide as many taxa respond to changes in environmental conditions,
particularly to changes in flow condition.
2.2.1 Additional Parameters
A number of additional water quality parameters were also selected for assessment
during the CRP. These parameters included particulate organic matter (POM),
dissolved organic matter (DOC), total suspended solids (TSS), water column Chl-a
and water column nutrients (Total Phosphorus, NH3-N, PO-4). These parameters were
to be measured at all experimental sites. Two Yeokal multiprobes were also used to
collect water column data throughout the study at the top and the bottom of the study
reach in the Mitta Mitta River.
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
2.3
Study Area
The study area covers a 60km reach of the regulated Mitta Mitta River, from
downstream of Lake Banimboola downstream to Tallandoon (Figure 2.1).
Figure 2.1: Location of the experimental sites (1 – 5) used during the project on Mitta Mitta
River and Snowy Creek. Includes flow gauging stations.
The Mitta Mitta River in the study area consists of armoured cobble benches and
sandy depositional zones and flows through two morphological zones: restricted
upland stream of moderate gradient and a meandering floodplain river channel of
reduced gradient (Blyth et al. 1984).
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
The river between Lake Banimboola and the confluence of Snowy Creek flows
through upland and foothills habitat, with steep-sided valleys dominated by dry
sclerophyll woodland. Downstream of the township of Mitta Mitta the river flows out
into a wide floodplain that has been extensively cleared for agriculture, and is
dominated by dairy and beef cattle enterprises (Koehn et al. 1995). In this lower
section the riparian zone is mostly cleared with occasional stands of River Red Gum
(Eucalyptus camaldulensis) and Willows (Salix spp.).
2.3.1 Hydrographic Data of the Mitta Mitta River and Snowy Creek
Flow conditions within the Mitta Mitta River are highly regulated by Dartmouth Dam.
The timing and duration of releases from Dartmouth are dependent upon the status of
the other major water storages in the River Murray system, particularly Hume
Reservoir.
Annual flow patterns within the Mitta Mitta are therefore highly variable and are
dependent on the status of water volumes in Dartmouth Dam and Hume Reservoir.
Average discharge (ML/day) during the period of December through February
gradually decreases at Colemans gauging station, but remains relatively constant at
the Tallandoon gauging station (Figure 2.2). Given that the flow in the Mitta Mitta
River is controlled by irregularly timed releases from Dartmouth Dam, high
variability in discharge exists between years (Figure 2.2).
Snowy Creek, used as a reference stream for this project, is an unregulated upland
tributary of the Mitta Mitta River (Section 2.4.3). The flow pattern of Snowy Creek
reflects natural rainfall and snow melt events within the creek’s catchment, and is
characterised by low flows in late summer and early autumn and high flows in late
winter and early spring, and has low variability between years.
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
10000
9000
8000
(ML/day)
7000
6000
Colemans
Tallandoon
Granite Flat
5000
4000
3000
2000
1000
0
19-Oct
2-Nov
16-Nov 30-Nov 14-Dec 28-Dec 11-Jan 25-Jan
8-Feb
22-Feb
7-Mar
Figure 2.2: Average daily flow (+SD, n=10) (megalitres per day) for the study period
(November to February) over the past ten seasons. Data recorded on the Mitta Mitta River at
Colemans and Tallandoon gauging stations and at Granite Flat on Snowy Creek.
2.3.2 Sites Locations and Descriptions
Five cobble benches, four on the Mitta Mitta River (site 1 – 4) and one on Snowy
Creek (site 5) were selected as experimental sites for the ecological assessment of
cyclic release patterns from Dartmouth Dam to the Mitta Mitta River (Figure 2.1).
Cobble benches were selected as experimental sites because these areas would
undergo considerable hydrological change during the CRP. Further, cobble benches
were common attributes along the study reach in the Mitta Mitta River and were also
abundant within Snowy Creek. A summary of site details and locations is presented in
Table 2.1.
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Table 2.1: Summary of site locations and details for the five sampling sites on the Mitta Mitta River and Snowy Creek
Site
No.
Rationale for site selection
Distance below
Dartmouth
Dam(river km)
AMG
ordinates
1
First accessible cobble bench
downstream of Lake Banimboola
used to assess ecological response
at the top of study area.
26
534206, 5956959
2
Downstream of the Snowy Creek
and Mitta Mitta River junction,
used to assess potential impacts
from inflows of major tributary.
28
533114, 5956322
3
In the mid-section of the study area
used
to
gauge
longitudinal
responses to variable flows.
45
4
Used to assess ecological response
to variable flows at the end of the
study area.
5
Snowy Creek downstream
Granite Flat gauging station.
To be used as a reference site.
of
co-
Mean Stream
Width
(m)
during low and
high flows
Low 20
High 50
Riverbed/
bench type
Habitats Available
Surrounding
Environment
and
Riparian Vegetation
Cobble and
coarse
gravel
- Permanently and
newly
inundated
cobble banks
-Littoral zone
Cleared grazing land.
Bottlebrush, tea-tree
and willow scattered
along banks.
Low 20
High 30
Cobble,
coarse
gravel and
sand
- Permanently and
newly
inundated
cobble banks
-Littoral zone
Open
eucalypt
woodland. Eucalypt,
Wattle, Tea-tree and
Willow along banks.
529971, 5964641
Low 30
High 50
Cobble,
coarse
gravel and
sand
- Permanently and
newly
inundated
cobble banks
-Littoral zone
Cleared grazing land.
Willow, poplars and
scattered
tea-tree
along banks.
60
518232, 5967211
Low 30
High 60
Cobble,
coarse
gravel and
sand
- Permanently and
newly
inundated
cobble banks
-Littoral zone
Cleared grazing land.
Willows and scattered
eucalypts
growing
along banks.
-
536704, 5953663
15
Cobble and
coarse
gravel
-Cobble bench
permanently
inundated areas
-Littoral zone
Open
eucalypt
woodland. Dense Teatree,
Wattle
and
Eucalypt along banks.
in
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
2.4
Project Design
The project was designed to assess the response of environmental indicators to
disturbance as a result of CRP by dividing the cobble bench at each experimental site
into two habitats: permanently inundated and newly inundated. Permanently
inundated - areas of the cobble bench that were inundated throughout the project (eg.
main Mitta Mitta River channel, background of Plate 2.1). Newly inundated - areas of
the cobble bench that were only inundated during periods of high flows (Plate 2.2).
Areas of cobble that are permanently inundated can be subject to disturbances from
factors such as scouring and reduced light availability during periods of high flow.
These disturbances can trigger altered successional pathways in biological
communities and create new habitat for colonising organisms. The design aimed to
assess the response of selected environmental indicators under permanent inundation
to variation in flow during the CRP and constant flow period that followed the
variable releases from Dartmouth Dam.
Plate 2.1: Mitta Mitta River at Site 1 showing exposed cobble bench during an 800 ML/day
flow, and channel in background 19/2/2002.
The inundation of instream and floodplain surfaces by increasing river height creates
a range of new habitats and opportunities for colonisation by instream organisms. The
experimental design aimed to assess the response of selected environmental indicators
in newly inundated habitats during the CRP.
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
Plate 2.2: Mitta Mitta River at Site 1 showing a newly inundated cobble bench during a 4500
ML/day flow, 18/12/2001.
2.4.1 Temporal Comparisons
The proposal intended to simulate three individual flood peaks (variable flow
releases) during the CRP (Table 1.1), followed by a period of constant flow
conditions. The project design aimed to record the response of environmental
indicators during each variable flow release, and then to compare each of the
consecutive flow releases to one another. Further, the project aimed to compare the
responses of environmental indicators during the CRP with those observed during the
constant flow period.
2.4.2 Longitudinal Comparisons
The proposal included the comparison of loads (kg/day) of POM and DOM between
site 1 and site 4. These comparisons allow the project to infer cumulative downstream
affects of the CRP in the Mitta Mitta River.
2.4.3 Reference Stream
Snowy Creek, the main tributary of the Mitta Mitta River below Dartmouth Dam was
selected as a reference site for the project. This creek system has an average annual
discharge of 577 ML/day (Figure 2.2, Plate 2.3). The creek is unregulated and its
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
catchment has undergone minimal anthropogenic disturbance. Selection criteria were
quite pragmatic for the project given time constraints, and included a system with
unregulated flow, moderate annual discharge with a close proximity to the Mitta Mitta
River. Snowy Creek met all selection criteria and was selected during a
reconnaissance trip to the study area.
Plate 2.3: Site 5 located on Snowy Creek, during a 900 ML/day flow, 2/12/2002
Environmental indicators (except for benthic metabolism) were assessed within
Snowy Creek during the study period at the same time as the assessment of sites on
the Mitta Mitta River. Given the flow conditions within Snowy Creek environmental
indicators were only assessed within permanently inundated sections of cobble bench.
2.4.4 Relevance of Reference Site
The inclusion of a reference site provided the opportunity to compare the response of
environmental indicators to variable flow conditions in the Mitta Mitta River to the
response of indicators within a reference system with unregulated flow conditions.
The reference site was used as an ecological target, to provide a relatively undisturbed
system that could be used to gauge the ecological response of variable flow conditions
in the Mitta Mitta River.
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
2.5
Sampling Regime
The sampling regime used during the study period was constructed to assess three
stages at day 2, 7-8 and 14-19 of each variable flow release: peak flow (~4800
ML/day), mid flow (~4000 ML/day) and base flow (~3200 ML/day)(Figure 3.1).
Table 2.2 provides a matrix showing sampling dates for each environmental indicator
and water quality parameters, and the habitats sampled. The newly inundated habitat
was only sampled on peak flow and mid flow. A total of nine sampling events took
place during the project, one on the final day of the first variable flow release, three
during the second and third variable flow release and two during the subsequent
constant flow period, which commenced on the 4th of January 2002.
Table 2.2: Sampling regime used during the ecological assessment of the cyclic release
pattern from Dartmouth Dam to the Mitta Mitta River, Victoria. Sampling commenced one day
prior to the second variable flow release on the 2/12/2001 and continued over 71 days until
the 11/02/2002. Perm denotes permanently inundated habitat; New denotes Newly inundated
habitat.
Date
Day
2/12/01
4/12/01
10/12/01
16/12/01
18/12/01
23/12/01
4/01/02
21/01/02
11/02/02
14
2
8
14
2
7
19
17
38
Cumulative Sample Water Water
Benthic biofilm Macroinvertebrates
Days
date
Quality Column
composition and
Enzyme
metabolism
activity
and
metabolism
Perm
New
Perm
New
0
1
2
2
8
3
14
4
16
5
21
6
33
7
50
8
71
9
2.5.1 Project Limitations
A major limitation of the project was the absence of before data describing the
ecological condition of the Mitta Mitta River prior to the commencement of the CRP.
The need for before data in restoration ecology is set out clearly in Underwood (1996)
and again in Chapman and Underwood (2000). RMW commenced the first variable
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
20
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
flow release on the 19/11/2001, and JC did not receive formal acceptance of its
proposal until the 26/11/2001. The lack of before data has placed major constraints
upon the statistical analyses and the strength of the conclusions and inferences that
could be drawn from the data recorded during the second and third variable flow
releases. Further, the subsequent lack of data from the first variable flow release
limited the project’s ability to infer the benefits of multiple flood pulses and the
introduction of variable releases following constant flow conditions.
The proposed flow regime set out in Table 1.1 was altered without notice during the
CRP (see Table 3.1). The alterations occurred during the peak of the third variable
flow release and the constant flow period. These anomalies limited comparisons that
could be made between peaks of each variable flow release and introduced variability
during the proposed constant flow period. The availability of one reference site and no
control site was seen as a limitation given that Chapman and Underwood (2000) state
that a restoration activity requires having a control and a reference site. This issue was
unavoidable given the logistics of sampling in a control stream, possibly within
another catchment and the short time frame for project preparation.
2.6
Predictions
2.6.1 Water Quality
1. The concentration of DOC, POC and suspended solids will increase during the
CRP compared to constant flows as a result of increased riverbank and floodplain
inundation and in channel resuspension. We predict there will be increased
loading of carbon and POM with distance downstream.
Water quality parameters listed in the tender will be used to aid in the interpretation of
biofilm composition and productivity and macroinvertebrate data.
2.6.2 Enzyme activity
1. Peak flows will increase the overall activity of water column bacteria, specifically
increase the activity of carbohydrase enzymes.
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
2. The CRP will increase the overall enzyme activity in the water column
(specifically increase the activity fatty acids and proteins) due to increased
riverbank and floodplain inundation and in channel resuspension. We predict there
will be increased overall enzyme activity with distance downstream.
2.6.3 Biofilm composition
Based on the results of Watts et al. (2001) we predict that if there are forty days of
constant low flows after the third variable flow release, the biofilms will reach a stable
state for biomass, composition and productivity. These data will be compared to the
data collected during the CRP.
1. Algal and total biomass from cobble substrata will decrease following peak flows
during the CRP compared to the biomass prior to the peak due to scouring from
increased velocity.
2. Peak flows will change the community composition of algal biofilms and promote
early successional algal taxa on cobble substrata due to scouring from increased
water velocity.
2.6.4 Benthic Metabolism
1. Peak flows will increase carbon respiration of biofilms on cobble substrata from
deep habitats due to scouring from increased water velocity and light deprivation
from increased water depth.
2. Newly inundated cobble with established biofilm communities will have increased
carbon production relative to those newly inundated cobbles that do not have an
established biofilm community.
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
2.6.5 Macroinvertebrates
The samples collected during the constant flow period following the third variable
flow release will be compared to the data collected during the CRP.
1. Variable flow releases will increase algal diversity on cobble substrata and will
result in a higher diversity of macroinvertebrates in cobble habitats.
2. Variable flow releases will increase algal diversity on cobble substrata and
increase the relative abundance of primary consumers on cobble habitats.
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
23
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
3.0 HYDROGRAPHIC DATA DURING STUDY PERIOD
Table 1.1 provides a summary of the proposed CRP from Dartmouth Dam to the Mitta
Mitta River. The CRP was to consist of three variable flow releases, commencing at
4000 ML/day, rising over two days to a 4800 ML/day flow peak, then receding over
twelve days to a minimum flow of 3200 ML/day (flows taken at Colemans gauge).
The three variable flow releases were then to be followed by a period of constant
flows of approximately 800 ML/day. This proposed pattern was not implemented as
substantial changes occurred. Table 3.1 provides a summary of the hydrographic data
recorded during the CRP, and is displayed in Figure 3.1. The major anomalies that
occurred were the extended peak of the third variable flow release which lasted four
days instead of the proposed one day, and a spike of 2500 ML/day that occurred
during the constant flow period.
Table 3.1. Summary of hydrographic data obtained from Colemans and Tallandoon gauging
stations during the CRP.
Variable flow release
1
2
3
Constant Flow Period
Duration (days)
14
14
18
45
Flow Rise (days)
2
2
2
Flow Recession (days)
12
12
14
Flow Peak (days)
1
1
4
Commencing Date
19.11.01
03.12.01
17.12.01
04.01.02
Maximum (ML/day)
4754
4684
4824
2490
Minimum (ML/day)
3200
3200
1518
590
Average
879
number
Colemans Gauge
Tallandoon Gauge
Maximum (ML/day)
5933
5387
5691
2540
Minimum (ML/day)
3859
3778
2186
1100
Average
1266
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
24
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
Figure 3.1: Hydrograph for the Mitta Mitta River recorded at Tallandoon and Colemans gauging stations, and Snowy Creek recorded at Granite Flat gauging
station for the period 1/11/2001 to 19/2/2002. See Figure 1.3 for locations of each gauging station. Hydrograph shows the position of the three variable flow
peaks and 12 day recession periods. VR denotes variable flow release.
Colemans gauge
Tallandoon gauge
Granite Flat gauge
7000
1st flow peak
2nd flow peak
6000
3rd flow peak
ML/day
5000
4000
3000
VR1
VR2
VR3
Constant Flow Period
2000
1000
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
25
14
/0
2/
02
7/
02
/0
2
31
/0
1/
02
24
/0
1/
02
17
/0
1/
02
10
/0
1/
02
3/
01
/0
2
27
/1
2/
01
20
/1
2/
01
13
/1
2/
01
6/
12
/0
1
29
/1
1/
01
22
/1
1/
01
15
/1
1/
01
8/
11
/0
1
1/
11
/0
1
0
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
4.0 WATER QUALITY
4.1
Introduction
As streams flood and subsequently inundate floodplain, fluxes of terrestrial organic
and inorganic materials occur between the floodplain and aquatic systems. Current
reviews show that these fluxes play significant roles in aquatic food webs (e.g.
Findlay & Sinsabaugh 1999; Robertson et al. 1999). Floodplain inundation also drives
changes in physico-chemical parameters by altering thermal, optical and chemical
properties within instream ecosystems.
A major component of floodplain to instream fluxes is dissolved organic matter
(DOM). DOM constitutes a large proportion of the organic carbon in all aquatic
ecosystems and is often a significant carbon resource for heterotrophic
microorganisms (predominantly bacteria)(Findlay & Sinsabaugh 1999). DOM plays a
significant role in aquatic food webs (Findlay et al. 1986), mediates the availability of
dissolved nutrients and metals (e.g. Carlson et al. 1993), and modifies the optical
properties of water bodies (Robertson et al. 1999).
Dissolved organic carbon (DOC) is the carbon component of DOM and in Australian
river systems is predominantly derived from the decomposition of leaf litter
(Robertson et al. 1999). Large quantities of DOC are leached from floodplain litter
during inundation, and drive instream productivity as floodwaters drain back into the
river channel.
Litter and soil borne organic nutrients are another component of the DOM flux that
occurs between floodplain and aquatic ecosystems during inundation (Baker et al.
2001; Mettler et al. 2001). Mineralised nitrogen (N) and phosphorus (P) from these
sources are generally the limiting factors for instream primary production. However,
recent research has shown that the quality of floodplain litter mediates the quantity of
nutrient mineralisation during inundation (Mettler et al. 2001).
Another important fraction of the material entrained by floodwaters is particulate
organic carbon (POM). POM is derived from a number of sources including coarse
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
26
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
particulate organic matter (CPOM), large woody debris (LWD), riparian soil particles,
flocculated DOC, scoured biofilms and autochthonous production (Ward 1986). POM
is a major food source for fine particle feeders (e.g. collector gatherers and filterers,
sensu Cummins & Klug 1979), these feeders being the dominant functional group in
many stream and river systems (Robertson et al. 1999).
The flux of floodplain carbon and nutrient sources to instream ecosystems during
inundation is also responsible for increases in water column and instream
productivity. Water column Chl-a and benthic biofilms are important food resources
for all functional feeding groups, and their availability controls the structure of
macroinvertebrate assemblages in stream and river systems (Matonickin et al. 2001).
Given the importance of DOC, POM, nutrient and water column Chl-a to instream
productivity, the project aimed to assess the response of these factors to the CRP from
Dartmouth Dam in the Mitta Mitta River, Victoria from December 2001 to February
2002. Further, physico-chemical parameters were also measured throughout the study
period as supporting data for assessments made upon environmental indicators. The
aim of this section is to examine the response of these parameters. The following
prediction can be made:
1. Concentrations of DOC, POM, organic and inorganic nutrients, total
suspended solids (TSS) and Chl-a will increase during periods of high flows
and decrease as flood waters recede.
4.2
Methods
4.2.1 Field Methods
Three replicate samples were taken from flowing surface waters at each study site on
each sampling event for determination of DOC, POM, TSS and water column Chl-a,
total phosphorus (TP), ammonia-nitrogen (NH3-N) and soluble reactive phosphorus
(PO-4) concentration. Two Yeokal multiprobes were placed near the water surface at
the top and bottom study site in the Mitta Mitta River. These probes recorded a
number of water column parameters every two hours.
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
27
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
4.2.2 Laboratory Methods
Particulate organic matter
Water column POM was measured using filtered (pre-weighed 70µm glass fibre
filters, GFF) water samples. The dry and ash weights of the filters plus retained
material were then used to estimate POM concentration’s per meter3.
Dissolved organic carbon
Water column DOC was measured using filtered (0.45µm) water samples and
analysed for the concentration of carbon (mg/L) using a Total Organic Carbon
Analyser.
Total suspended solids
TSS was calculated using the dry and ash weights obtained during the POM analysis.
TSS was calculated as the total dry weight of filtrate and estimated as g/m3.
Chlorophyll-a
Water column Chl-a was measured using filtered (70µm GFF) water samples. The
Chl-a was fixed by placing filters and retained material into 10ml vials containing a
solution of 150mg of magnesium carbonate and 8mL of 90% aqueous methanol.
Following refrigeration vials were centrifuged and the resulting supernatant was
analysed for light absorbance at 750 and 666λm using a light spectrophotometer. One
hundred microlitres (100µL) of 4 percent hydrochloric acid was then added to the
supernatant and the absorbance of light was measured again at 750 and 666λm for the
determination of phaeophytin concentrations.
Nutrient (TP, NH3-N, PO-4)
Total phosphorus (TP) concentration was measured using an Inductively Coupled
Plasma Atomic Emission Spectrometer (ICP). Ammonia – Nitrogen (NH3-N) and
Phosphate (PO-4) concentrations were measured using a Segmented Flow Auto
Analyser (ALCHEM) at the Environmental and Analytical Laboratory at Charles
Sturt University (NATA accredited).
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
28
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
4.2.3 Data Manipulation and Analysis
The water quality parameters (except data from the Yeokal multiprobes) have been
summarised by the calculation of mean and standard deviation on a per site basis. The
comparison of parameters at each site utilised visual interpretation of differences. The
absence of replication in the data from the Yeokal multiprobes meant that
interpretation was also visually compared but without calculated mean and standard
deviation.
Concentrations of DOC and POM at sites 1 and 4 were multiplied by discharge
(ML/day) at Colemans and Tallandoon gauging stations respectively to attain a daily
load (kg/day) of each parameter at each site and on each sampling date. An organic
matter budget for the study reach was calculated for DOC and POM concentrations
for each sampling date by subtracting the loads at site 4 from site 1.
4.3
Results
4.3.1 POM, DOC, TSS and Chl-a
The concentration of POM at each site in the Mitta Mitta River increased during the
peak of the second variable flow release (date 2) (Figure 4.1). These changes were
most pronounced at sites 3 and 4 with increases of 22 and 24 g/m3, respectively. POM
concentration in the reference stream varied little during this period.
The peak of the third variable flow release (date 5) resulted in a substantial decrease
in POM at sites 1, 2 and 4, but an increase at site 3. POM increased at all sites during
the recession of the third variable flow release, and then gradually decreased to less
than 8 g/m3 at the end of the constant flow period. POM at the reference site followed
a similar trend gradually decreasing over time to its lowest concentration on date 9.
The contribution of POM from the reference stream to the Mitta Mitta River does not
appear to be substantial given the minor difference in concentrations between sites
one and two.
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
29
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
40.00
Site 1
g/m3
30.00
20.00
10.00
2/
12
/0
1
9/
12
/0
1
16
/1
2/
01
23
/1
2/
01
30
/1
2/
01
6/
01
/0
2
13
/0
1/
02
20
/0
1/
02
27
/0
1/
02
3/
02
/0
2
10
/0
2/
02
0.00
40.00
Site 2
g/m3
30.00
20.00
10.00
2/
12
/0
1
9/
12
/0
1
16
/1
2/
01
23
/1
2/
01
30
/1
2/
01
6/
01
/0
2
13
/0
1/
02
20
/0
1/
02
27
/0
1/
02
3/
02
/0
2
10
/0
2/
02
0.00
40.00
Site 3
g/m3
30.00
20.00
10.00
2/
12
/0
1
9/
12
/0
1
16
/1
2/
01
23
/1
2/
01
30
/1
2/
01
6/
01
/0
2
13
/0
1/
02
20
/0
1/
02
27
/0
1/
02
3/
02
/0
2
10
/0
2/
02
0.00
40.00
Site 4
g/m3
30.00
20.00
10.00
2/
12
/0
1
9/
12
/0
1
16
/1
2/
01
23
/1
2/
01
30
/1
2/
01
6/
01
/0
2
13
/0
1/
02
20
/0
1/
02
27
/0
1/
02
3/
02
/0
2
10
/0
2/
02
0.00
40.00
Site 5
g/m3
30.00
20.00
10.00
2/
02
10
/0
/0
2
3/
02
1/
02
27
/0
1/
02
20
/0
1/
02
13
/0
/0
2
6/
01
2/
01
30
/1
2/
01
23
/1
2/
01
16
/1
/0
1
9/
12
2/
12
/0
1
0.00
Figure 4.1: Water column concentrations (g/m3) of particulate organic matter (POM) at sites 1
to 4 on the Mitta Mitta River and site 5 on Snowy Creek (reference site) on nine sample dates
from December 2001 to February 2002 (mean ± SD, n=3).
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
30
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
The concentration of DOC was generally low at all sites on the Mitta Mitta River and
in the reference stream throughout the study period (Figure 4.2). There were no
substantial changes in DOC concentration at the reference site during the study period
although an increase in DOC concentration at the recession of the third variable flow
release was consistent with increases found at all sites on the Mitta Mitta River during
the same period. DOC decreased slightly at sites 1, 2 and 4 following the flow peaks
of the second (date 2) and third (date 5) variable flow release. All Mitta Mitta sites
showed substantial increases in DOC during the recession period of the third variable
flow release (dates 6 and 7), which then gradually decreased during the constant flow
period.
TSS increased substantially at all sites on the Mitta Mitta River during the peak flow
of the second variable flow release (date 2) and a minimal increase in TSS in the
reference stream was also evident at this time. TSS concentrations varied little at sites
1 and 2 on the Mitta Mitta River as well as in the reference stream following date 2
and until the end of the constant flow period (Figure 4.3). TSS at sites 3 and 4 in the
Mitta Mitta decreased rapidly during the recession of the second variable flow release
(dates 3 and 4), and increased again during the peak flow of the third variable flow
release. TSS concentrations were maintained above 30 g/m3 at sites 3 and 4 on the
Mitta Mitta until midway through the constant flow period and then decreased
gradually to the end of the study.
Chl-a concentrations increased substantially at all sites on the Mitta Mitta River
during the peak of the second variable flow release (date 2). Only at sites 2, 3 and 4
recorded increased Chl-a concentrations during the peak of the third variable flow
release (Figure 4.4). The concentration of Chl-a decreased rapidly at all Mitta Mitta
River sites during the recession period of both variable flow releases. The reference
stream did not follow a similar pattern in Chl-a concentration to sites on the Mitta
Mitta, varying little at approximately 300µg/m3 throughout the study period.
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
31
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
30.00
mg/L
Site 1
20.00
10.00
2/
12
/0
1
9/
12
/0
1
16
/1
2/
01
23
/1
2/
01
30
/1
2/
01
6/
01
/0
2
13
/0
1/
02
20
/0
1/
02
27
/0
1/
02
3/
02
/0
2
10
/0
2/
02
0.00
30.00
mg/L
Site 2
20.00
10.00
2/
12
/0
1
9/
12
/0
1
16
/1
2/
01
23
/1
2/
01
30
/1
2/
01
6/
01
/0
2
13
/0
1/
02
20
/0
1/
02
27
/0
1/
02
3/
02
/0
2
10
/0
2/
02
0.00
30.00
mg/L
Site 3
20.00
10.00
2/
12
/0
1
9/
12
/0
1
16
/1
2/
01
23
/1
2/
01
30
/1
2/
01
6/
01
/0
2
13
/0
1/
02
20
/0
1/
02
27
/0
1/
02
3/
02
/0
2
10
/0
2/
02
0.00
30.00
mg/L
Site 4
20.00
10.00
2/
12
/0
1
9/
12
/0
1
16
/1
2/
01
23
/1
2/
01
30
/1
2/
01
6/
01
/0
2
13
/0
1/
02
20
/0
1/
02
27
/0
1/
02
3/
02
/0
2
10
/0
2/
02
0.00
mg/L
30.00
Site 5
20.00
10.00
10
/0
2
/0
2
/0
2
02
3/
/0
1
/0
2
/0
2
27
/0
1
20
/0
1
/0
2
/0
2
13
01
6/
30
/1
2
/0
1
/0
1
/1
2
23
16
/1
2
/0
1
/0
1
12
9/
2/
12
/0
1
0.00
Figure 4.2: Water column concentrations (mg/L) of dissolved organic carbon (DOC) at sites 1
to 4 on the Mitta Mitta River and site 5 on Snowy Creek (reference site) on the nine sample
dates from December 2001 to February 2002 (mean ± SD, n=3).
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
32
70.00
60.00
50.00
40.00
30.00
20.00
10.00
0.00
Site 1
2/
12
/0
1
9/
12
/0
1
16
/1
2/
01
23
/1
2/
01
30
/1
2/
01
6/
01
/0
2
13
/0
1/
02
20
/0
1/
02
27
/0
1/
02
3/
02
/0
2
10
/0
2/
02
g/m3
70.00
60.00
50.00
40.00
30.00
20.00
10.00
0.00
g/m3
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
70.00
60.00
50.00
40.00
30.00
20.00
10.00
0.00
Site 3
70.00
60.00
50.00
40.00
30.00
20.00
10.00
0.00
Site 4
70.00
60.00
50.00
40.00
30.00
20.00
10.00
0.00
10
/0
2
/0
2
/0
2
02
3/
/0
2
/0
1
27
/0
1
/0
2
/0
2
20
/0
1
/0
2
13
01
6/
/0
1
/1
2
30
23
/1
2
/0
1
/0
1
/1
2
16
12
/0
1
Site 5
9/
2/
12
/0
1
g/m3
2/
12
/0
1
9/
12
/0
1
16
/1
2/
01
23
/1
2/
01
30
/1
2/
01
6/
01
/0
2
13
/0
1/
02
20
/0
1/
02
27
/0
1/
02
3/
02
/0
2
10
/0
2/
02
g/m3
2/
12
/0
1
9/
12
/0
1
16
/1
2/
01
23
/1
2/
01
30
/1
2/
01
6/
01
/0
2
13
/0
1/
02
20
/0
1/
02
27
/0
1/
02
3/
02
/0
2
10
/0
2/
02
g/m3
2/
12
/0
1
9/
12
/0
1
16
/1
2/
01
23
/1
2/
01
30
/1
2/
01
6/
01
/0
2
13
/0
1/
02
20
/0
1/
02
27
/0
1/
02
3/
02
/0
2
10
/0
2/
02
Site 2
Figure 4.3: Water column concentrations (g/m3) of total suspended solids (TSS) at sites 1 to
4 on the Mitta Mitta River and site 5 on Snowy Creek (reference site) on the nine sample
dates from December 2001 to February 2002 (mean ± SD, n=3).
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
33
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
1200
Site 1
ug/m3
900
600
300
2/
12
/0
1
9/
12
/0
1
16
/1
2/
01
23
/1
2/
01
30
/1
2/
01
6/
01
/0
2
13
/0
1/
02
20
/0
1/
02
27
/0
1/
02
3/
02
/0
2
10
/0
2/
02
0
1200
Site 2
ug/m3
900
600
300
2/
12
/0
1
9/
12
/0
1
16
/1
2/
01
23
/1
2/
01
30
/1
2/
01
6/
01
/0
2
13
/0
1/
02
20
/0
1/
02
27
/0
1/
02
3/
02
/0
2
10
/0
2/
02
0
1200
Site 3
ug/m3
900
600
300
2/
12
/0
1
9/
12
/0
1
16
/1
2/
01
23
/1
2/
01
30
/1
2/
01
6/
01
/0
2
13
/0
1/
02
20
/0
1/
02
27
/0
1/
02
3/
02
/0
2
10
/0
2/
02
0
1200
Site 4
ug/m3
900
600
300
2/
12
/0
1
9/
12
/0
1
16
/1
2/
01
23
/1
2/
01
30
/1
2/
01
6/
01
/0
2
13
/0
1/
02
20
/0
1/
02
27
/0
1/
02
3/
02
/0
2
10
/0
2/
02
0
1200
Site 5
ug/m3
900
600
300
/0
2
/0
2
/0
2
10
02
3/
27
/0
1
/0
2
/0
2
/0
1
20
/0
1
/0
2
/0
2
13
01
6/
/1
2
/0
1
/0
1
30
/1
2
23
/1
2
/0
1
/0
1
16
12
9/
2/
12
/0
1
0
Figure 4.4: Water column concentrations (ug/m3) of chlorophyll-a (Chl-a) at sites 1 to 4 on the
Mitta Mitta River and site 5 on Snowy Creek (reference site) on the nine sample dates from
December 2001 to February 2002 (mean ± SD, n=3).
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
34
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
4.3.2 Yeokal Multiprobes
Te m p o C
S i te 1
C o n d u S /c m
6 0
oC, uS/cm, mg/L
5 0
1 0
D O
9
p H
m g /L
8
7
4 0
5
pH
6
3 0
4
2 0
3
2
1 0
1
1
17
:5
3:
00
12
/0
2/
02
5/
02
/0
2
17
:5
3:
00
17
:5
3:
00
29
/0
1/
02
22
/0
1/
02
17
:5
3:
00
17
:5
3:
00
15
/0
1/
02
7/
01
/0
2
10
:1
5:
00
2
10
:1
5:
00
31
/1
2/
0
24
/1
2/
01
10
:1
5:
00
10
:1
5:
00
1
0
17
/1
2/
01
0
Te m p o C
S i te 4
C o n d u S /c m
60
oC, uS/cm, mg/L
50
1 0
D O m g /L
9
p H
8
7
40
5
pH
6
30
4
20
3
2
10
1
2/
/0
12
5/
00
00
17
17
:5
:5
3:
3:
00
3:
:5
17
02
2
/0
02
1/
/0
29
22
00
3:
17
:5
3:
:5
17
02
02
1/
/0
1/
/0
15
00
00
5:
:1
10
2
:1
5:
10
1
02
/0
2
7/
/1
31
00
24
00
5:
:1
10
01
2/
01
2/
/1
2/
/1
17
00
5:
:1
10
01
0
01
0
Figure 4.5: Yeokal multiprobe data collected from site 1 and site 4 from 16th of December 2001 to 12th of February 2002. Multiprobes recorded temperature in
degrees Celius, Conductivity (µS/cm), dissolved oxygen (DO) concentration (mg/L) and pH.
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
35
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
The pH, conductivity (µS/cm) and temperature (oC) were lower and dissolved oxygen
concentration (DO) was higher at site 1 during the CRP compared to the constant flow
period (Figure 4.5). The pH increased from 7.5 to 8.5 over the course of the study,
while conductivity and temperature recorded a minimal increase of approximately
7µS/cm and 3oC, respectively. Temperature and DO displayed strong diurnal
fluctuations.
Conductivity and pH varied little at site 4 in the period following the CRP.
Temperature was slightly lower during the variable flow releases when compared to
the constant flow period. DO concentration also decreased at site 4 following the
CRP, from approximately 11 mg/L to around 7 mg/L at the end of the constant flow
period.
4.3.3 Water Column Nutrient
Water column nutrient concentrations were exceptionally low at all sites on the Mitta
Mitta River and Snowy Creek for the duration of the study period (Table 4.1). The
majority of samples collected were below the detectable limits for the each of the
three nutrients analysed (PO-4, NH3-N and TP). Those samples that were above the
detectable limits displayed very low concentrations
4.3.4 DOC and POM Loading
Water column loads of POM were consistently higher at site 4 when compared to site
1. This indicates organic matter inputs from floodplain inundation, scouring of
substrata or runoff from influent streams occur along the length of the Mitta Mitta
River study area (Figure 4.6a).
The peak flow of the second variable flow release led to a rise in POM at both sites
peaking at 146.03 ± 11.54 kg/day and 65.75 ± 3.54 at sites 4 and 1 respectively
(Figure 4.6a). The peak flow of the third variable flow release led to a substantial
decrease in POM at both sites, which then increased to date 8, the midpoint of the low
constant flow period.
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
36
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
Table 4.1: Summary of Nutrient analyses upon PO-4, NH3-N and TP for sites 1 to 4 on the
Mitta Mitta River, and site 5 on the reference stream Snowy Creek for nine sampling dates
from December 2001 to February 2002 (mean ± SD, n=3). <0.02 denotes undetectable limits
for PO-4 and TP. <0.05 denotes undetectable limits for NH3-N. Highlighted values represent
samples above detectable limits.
PO-4
Date
02/12/01
04/12/01
10/12/01
16/12/01
18/12/01
23/12/01
04/01/02
21/01/02
06/02/02
NH3-N
Date
02/12/01
04/12/01
10/12/01
16/12/01
18/12/01
23/12/01
04/01/02
21/01/02
06/02/02
TP
Date
02/12/01
04/12/01
10/12/01
16/12/01
18/12/01
23/12/01
04/01/02
21/01/02
06/02/02
Site
1
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
2
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
0.02 ± 0.00
3
<0.02
<0.02
<0.02
<0.02
0.03 ± 0.01
<0.02
<0.02
<0.02
<0.02
4
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
5
<0.02
<0.02
<0.02
0.02 ± 0.00
0.07 ± 0.05
<0.02
<0.02
<0.02
<0.02
1
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
2
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
3
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
4
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
5
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
<0.05
1
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
Site
2
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
<0.02
0.02 ± 0.00
3
<0.02
<0.02
<0.02
<0.02
0.05 ± 0.04
<0.02
<0.02
<0.02
<0.02
4
<0.02
<0.02
<0.02
0.02 ± 0.00
<0.02
<0.02
<0.02
<0.02
<0.02
5
<0.02
<0.02
<0.02
0.02 ± 0.00
0.09 ± 0.07
<0.02
0.04 ± 0.2
<0.02
<0.02
Site
Loads of DOC displayed only minimal differences between sites 1 and 4 (Figure
4.6b). DOC loads were consistently higher at site 4 except on date 3 following the
peak of the second variable flow release. DOC loads were lowest under low flow
conditions and during this time displayed similar concentrations to POM. DOC
concentrations decreased on the flow peak of the second variable flow release at both
sites, but increased at site 1 and decreased at site 4 by date 5 the peak of the third
variable flow release. Maximum DOC loads at both sites occurred on date 6, the
midpoint of the third variable flow release recession of 38.17 ± 6.58 kg/day at site 1
and 65.75 ± 3.54 at site 4.
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
37
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
Net gain of POM in the water column increased during the second variable flow
release but decreased rapidly with the onset of the third variable flow release peak
(Figure 4.6c). Net DOC decreased during each peak flow event of the CRP suggesting
there is a dilution of DOC in river water by water from Dartmouth Dam. DOC was
negative on date 3 following the second variable flow release peak showing there was
a net loss of DOC in the system under those flow conditions. Under constant flow
conditions both DOC and POM consistently recorded net gains.
4.4
Discussion
4.4.1 Water Quality Parameters
The effects of the CRP in the Mitta Mitta River on the movement of DOC, POM, TSS
and water column Chl-a were examined. It was predicted there would be an overall
increase in concentrations of these four parameters during the peak discharges of the
CRP in the Mitta Mitta River compared to the reference stream.
The results of this study have shown a general trend of a short-term increase for all
parameters (except DOC) during the second variable flow release peak that was not
evident in any parameter measured in the reference stream during the same period.
Water column Chl-a, TSS and DOC concentrations also showed similar increases
during the peak of the third variable flow release and again this was not evident in the
reference stream.
The increases in water column Chl-a during each variable flow release peak is
suspected to be the result of scouring activity caused by increased flow velocity. The
scouring process can be a positive influence to the ecological health of stream
environments by resetting benthic biofilm successions, a process which increases the
algal species diversity and habitat available for consumers.
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
38
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
180
160
Site 1
Site 4
140
kg POM/day
120
100
80
60
40
20
10
/0
2/
02
3/
02
/0
2
27
/0
1/
02
20
/0
1/
02
13
/0
1/
02
6/
01
/0
2
30
/1
2/
01
23
/1
2/
01
16
/1
2/
01
9/
12
/0
1
2/
12
/0
1
0
60
Site 1
50
Site 4
kg DOC/day
40
30
20
10
10
/0
2/
02
3/
02
/0
2
27
/0
1/
02
20
/0
1/
02
13
/0
1/
02
6/
01
/0
2
30
/1
2/
01
23
/1
2/
01
16
/1
2/
01
9/
12
/0
1
2/
12
/0
1
0
120
kg POM and DOC/day
100
POM
DOC
80
60
40
20
10
/0
2/
02
3/
02
/0
2
27
/0
1/
02
20
/0
1/
02
13
/0
1/
02
6/
01
/0
2
30
/1
2/
01
23
/1
2/
01
16
/1
2/
01
-20
9/
12
/0
1
2/
12
/0
1
0
Figure 4.6: Mean (± SD) loadings of (a) POM and (b) DOC per day at sites 1 and 4 on the
Mitta Mitta River, and (c) a reach scale budget of POM and DOC between sites 1 and 4 on
the Mitta Mitta River.
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
39
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
The first variable flow release which was not measured in this study may have
resulted in the entrainment and flux of larger quantities of organic matter than were
observed during the second and third variable flow releases. The primary inundation
caused by the first peak flow may have caused a major breakdown and movement of
floodplain and instream sources of POM and DOC, resulting in a loss of quality and
quantity of these sources in the river system.
There were no obvious cumulative effects of successive variable flow releases on
concentrations of the four water quality parameters measured downstream of site 2.
These results suggest that continuous input of organic matter does not occur below the
Mitta Mitta and Snowy Creek confluence. The floodplain downstream of the township
of Mitta Mitta has been cleared for agricultural development, resulting in a narrow
riparian corridor dominated by Salix spp, an introduced deciduous tree with a defined
seasonal pulse of litter fall. Subsequently, the quantity and quality of floodplain
organic matter has been substantially altered and thus flow peaks in the study area
may not result in relatively large and consistent accumulations of organic matter
entrained into the water column.
Nutrient concentrations in the Mitta Mitta River and Snowy Creek were extremely
low throughout the study period, indicating a regional trend of low nutrient levels in
flowing surface waters. Further, the results from the Mitta Mitta River also
demonstrate that the water released from Dartmouth Dam is also very low in the
concentrations of the analysed nutrients. Trace nutrient levels in flowing surface water
within the region and from Dartmouth Dam coupled with a lack of quality floodplain
litter may result in minimal transport and or availability of organic and inorganic
nutrient within the Mitta Mitta River.
The CRP did not result in any distinct changes in the physicochemical parameters
measured at reaches located at the top and bottom of the study area. However, the
onset of constant flow conditions within the Mitta Mitta River resulted in an increase
in water column conductivity, pH and temperature and a decrease in DO
concentration. It is suspected that the reductions in DO concentrations may be a result
of a high benthic oxygen demand generated by the senescence of benthic biofilm
communities. This is evidenced by the presence of layers of dead algae within the
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
40
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
river following prolonged low flows. Increases in temperature are probably the result
of changes in season from November to February, decreased discharge levels and
flow rates as well as decreased water depth, allowing greater exposure to solar
warming. Increases in conductivity and pH during the constant flow conditions may
be due to increased contribution from ground water sources to the main river channel
relatively to water from Dartmouth Dam.
4.4.2 DOC and POM Loading
The loads of POM and DOC were relatively low, but consistent with loads recorded
from similar headwater stream systems (Webster & Meyer 1997). Water column loads
of POM were consistently higher at site 4 than at site 1, indicating that organic matter
inputs from floodplain inundation, scouring of substrata or runoff from influent
streams occur along the entire Mitta Mitta River study area. This process appears to
occur under the range of flow conditions experienced during this study as the organic
matter budget showed net POM to be consistently positive. The constant flow period
was characterised by reduced loadings of POM at both sites indicating minimal
scouring or input from influent streams occurred under these flow conditions.
Loads of DOC displayed only minimal differences between sites 1 and 4. These
trends indicate that either the input of DOC is not continuous along the study area or,
that it is rapidly utilised by bacteria and does not accumulate in the water column.
Similarly, net DOC decreased on each variable flow release peak indicating there is a
dilution of DOC in river water by water from Dartmouth Dam.
4.5
•
Summary of Findings
The release of peak flows of 4800 ML/day during the second and third variable
flow release resulted in short-term increases in the concentration of water column
organic matter in the form of DOC, POM, TSS and Chl-a.
•
Periods of constant flow conditions decreased the concentrations of water column
organic matter.
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
41
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
•
Increased concentrations of instream Chl-a following the peak flows of each
variable flow release may be the result of scouring caused by increased flow
velocity on benthic biofilms.
•
The lack of data from the first variable flow release makes interpretation of the
concentrations of each parameter very difficult as potential organic matter sources
may have been degraded and or removed during the first variable flow release.
•
There were extremely small concentrations of water column nutrients within all
sites on the Mitta Mitta River and Snowy Creek.
•
Constant flow conditions resulted in increases in water column temperature, pH
and conductivity and decreased DO concentration.
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
42
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
5.0 WATER
COLUMN
EXTRACELLULAR
ENZYME
ACTIVITY
5.1
Introduction
Heterotrophic microorganisms (predominantly bacteria) form a key level in aquatic
ecosystems, being supported by DOM. Bacterial communities in aquatic habitats can be
derived from either aquatic or terrestrial habitats, although terrestrial bacteria do not
survive for extended periods in aquatic habitats (Veal et al. 1998). Bacterial communities
can occur in all aquatic habitats but are abundant in the water column and surface
sediments. Bacteria are responsible for the biogeochemical cycling of all elements in the
biosphere (Hart et al. 1996). They are generally considered as key organisms responsible
for the decomposition of organic material and the regeneration of nutrients. The
composition and productivity of aquatic bacterial communities are the consequence of
multiple interactions between hydrological, chemical and biotic factors. Bacteria have been
extensively used as indicators of pollution such as contamination by heavy metals. More
recently there has been a focus on developing microbial indicators as measures of
ecosystem function, where the aim is to measure the activity of key microbial processes.
Carbon compounds in aquatic environments are utilised by bacteria through the release of
extracellular enzymes. A technique has been developed which uses the activity of bacterial
extracellular enzymes to link bacterial productivity to the concentrations and classes of
available organic matter. (Sinsabaugh et al. 1997). Organic matter in aquatic systems
occurs as carbohydrates, proteins, fatty acids and other compounds. Each class of organic
matter requires a specific extracellular enzyme to be excreted from bacteria in order for the
organic matter to be utilised. Bacteria can shift their composition of extracellular enzymes
in response to changes in the classes of available organic matter. This technique has
successfully been used to identify the response of microbial metabolism, composition and
utilisation of organic matter to disturbance in a wide variety of aquatic habitats (Chappell
& Goulder 95; Boschker & Cappenberg 1998; Findlay et al. 2001) and in Australian river
systems by Burns & Ryder (2001a). By monitoring these shifts in enzyme activity it is
possible to examine the classes and quantity of organic matter available to these microbial
communities.
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
43
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
The aim of this section is to examine the response of water column bacterial activity to a
CRP from Dartmouth Dam to the Mitta Mitta River, Victoria from December 2001 to
February 2002. The following prediction can be made:
1. There will be an overall increase in rates of water column bacterial enzyme
activity during the peak discharges of the CRP from Dartmouth Dam to the Mitta
Mitta River.
5.2
Methods
5.2.1 Field methods
Five replicate water samples were taken from flowing surface waters at each study site on
each sampling event for determination of extracellular enzyme activity. Samples were
collected and stored in 30ml polycarbonate vials and frozen immediately after collection.
5.2.2 Laboratory Methods
The following methylumbelliferyl (MUF) labelled carbon substrates were used to estimate
bacterial activity in water samples (1) 4-MUF-butyrate (fatty acid esterase – FAE); (2) αD-glucosidase (carbohydrate), (3) β-D-glucosidase (carbohydrate); (4) β-D-xylosidase
(long chain carbohydrate, eg. woody substrates), and (5) Leucine-7-amino-4-methylcoumarin (aminopeptidase). These enzymes are involved in the degradation of
polysaccharides, carbohydrates and proteins derived from a range of autochthonous and
allocthonous organic matter (Chrost 1991).
Stock solutions (1mM) of each MUF-linked substrate were made and diluted to known
concentrations that assume substrate saturation (50-100µM) for each water sample. Water
samples were defrosted and activities were assayed by mixing 750 µL of each substrate
with 750 µL of sample water in 3ml disposable fluorometric cuvettes and conducted at
20oC. Four replicate samples of river water from each site for each of the sampling dates
(Table 2.2) were analysed using this technique. The α- β- glucosidases and xylosidase
were assayed at pH 8 in 5mM bicarbonate buffer, and esterase and aminopeptidase in pH 7
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
44
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
5mM phosphate buffer. Fluorescence was read repeatedly over a 1 to12 hour period at
365nm excitation and 450nm emission on a Shimadzu Fluorometer.
5.2.3 Data Manipulation and Analysis
Enzyme activities are expressed as rates of accumulation of MUF equivalents (µmol/L/h),
by using the emission coefficient calculated by regression from MUF standards in
bicarbonate buffer and phosphate buffer. Individual samples were corrected for substrate
degradation using a boiled replicate water sample. All data were log10 transformed to
remove dependencies between mean and variance.
Statistical analysis employed single factor ANOVA planned comparisons of date 1 (end of
first variable flow release) to date 2 (peak flow of second variable flow release) and date 4
(end of second variable flow release) to date 5 (peak flow of third variable flow release) for
each of the five sites using Statistica V4 (Statistica 1995). This design is based on the rapid
and short term response of the enzyme activities to changes in discharge and tests the
response of each enzyme at each site to the predicted increases in DOM during the flood
peaks.
5.3
Results
Activities of all enzymes were generally highest during the peak discharges of the second
and third variable flow releases, although trends often differed between the two releases
and between sites for each enzyme. Very low activities were recorded from all sites on the
Mitta Mitta River throughout the period of low and constant flows (dates 7 to 9). Enzyme
activities at the reference site on Snowy Creek were consistently low, with no significant
difference in activities found between the sampling dates examined (Table 3.1).
The two carbohydrase enzymes, alpha and beta glucosidase displayed significant increases
in activity at all sites during the third variable flow release, with activities increasing with
distance downstream (Table 5.1, Figures 5.1, 5.2). Activities ranged from 1.56 ± 0.09
µM/L/h at site 1 to 2.64 ± 0.46 µM/L/h at site 4 for alpha glucosidase and 0.54 ± 0.02
µM/L/h at site 2 to 1.33 ± 0.34 µM/L/h at site 4 for beta glucosidase. However the second
variable flow release did not result in such a consistent response across sites. Significant
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
increases in alpha and beta glucosidase enzyme activity from dates 1 to 2 were only found
at site 1.
Table 5.1: Probability value and significance levels of planned comparison one-way ANOVAs
comparing enzyme activities of river water from dates 1 to 2, and 4 to 5 at four sites in the Mitta
Mitta River (sites 1 to 4) and in Snowy Creek (site 5). Post hoc tests indicating direction of trend are
shown in brackets. * = P < 0.05, ** = P < 0.01, *** = P < 0.001.
Release 2
(Dates 1 to 2)
Alpha glucosidase
Site 1
Mitta Mitta
0.001 *** (1<2)
Site 2
Mitta Mitta
0.263
Site 3
Mitta Mitta
0.814
Site 4
Mitta Mitta
0.381
Site 5
Snowy Creek
0.613
Beta glucosidase
0.001 *** (1<2)
0.039 *
0.016 * (1>2)
0.026 * (1>2)
0.061
Butyrate
0.087
0.001 *** (1<2)
0.714
0.072
0.803
Leucine
0.138
0.515
0.113
0.048 * (1<2)
0.347
Xyloside
0.903
0.888
0.790
0.693
0.746
Release 3
Dates (4 to 5)
Alpha glucosidase
Site 1
Mitta Mitta
0.001 *** (4<5)
Site 2
Mitta Mitta
0.001 *** (4<5)
Site 3
Mitta Mitta
0.001 *** (4<5)
Site 4
Mitta Mitta
0.001 *** (4<5)
Site 5
Snowy Creek
0.464
Beta glucosidase
0.008 ** (4<5)
0.021 *
(4<5)
0.001 *** (4<5)
0.001 *** (4<5)
0.084
Butyrate
0.212
0.004 ** (4>5)
0.010 ** (4>5)
0.613
0.771
Leucine
0.106
0.041 *
0.184
0.001 *** (4<5)
0.355
Xyloside
0.093
0.084
0.006 ** (4<5)
0.002 ** (4<5)
0.887
(1>2)
(4>5)
Differences in the responses of the other enzymes were not as definitive as the
carbohydrase enzymes due to small variations in their response to altered flow regimes and
large standard deviations. Although not significantly different at all sites, the butyrate
(fatty acid esterase) and leucine (protein) substrates displayed trends of higher activity
during the second Release and lower activity during the third Release (except site 4)
(Figures 5.3, 5.4). This indicates they may have potential for detecting change in microbial
production with increased replication. Xyloside activities were very low compared to the
other substrates indicating low concentrations of long chain carbohydrates (derived from
woody debris) in the water column (Figure 5.5).
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
4.0
Alpha Glucoside
site1
site2
site4
site5
site3
3.5
uM substrate/L/h
3.0
2.5
2.0
1.5
1.0
0.5
02
2
2/
20
/0
10
31
/0
5/
02
/2
1/
20
00
02
02
/0
26
1/
20
1/
20
02
02
21
11
16
/0
/0
1/
20
/0
/2
1/
20
02
2
00
2
6/
01
/2
1/
01
2/
20
00
01
01
27
/1
/1
22
2/
20
17
/1
/1
12
2/
20
01
01
2/
20
00
/2
7/
12
2/
12
/2
00
1
1
0.0
Figure 5.1: Alpha glucosidase activities in µM substrate/L/h at sites 1 to 4 on the Mitta Mitta River
and site 5 on Snowy Creek (reference site) on the nine sample dates from December 2001 to
February 2002 (mean ± SD, n=4).
4
Beta Glucosidase
site1
site2
site4
site5
site3
3.5
2.5
2
1.5
1
0.5
10
/0
2/
20
02
02
/2
0
02
3/
27
/0
1/
20
02
02
1/
20
20
/0
13
/0
1/
20
02
02
6/
01
/2
0
01
30
/1
2/
20
01
2/
20
23
/1
16
/1
2/
20
01
01
/2
0
12
9/
12
/2
0
01
0
2/
uM substrate/L/h
3
Figure 5.2: Beta glucosidase activities in µM substrate/L/h at sites 1 to 4 on the Mitta Mitta River
and site 5 on Snowy Creek (reference site) on the nine sample dates from December 2001 to
February 2002 (mean ± SD, n=4).
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
4
Butyrate
site1
site2
site4
site5
site3
3.5
uM substrate/L/h
3
2.5
2
1.5
1
0.5
10
/0
2/
20
02
3/
02
/2
00
2
27
/0
1/
20
02
20
/0
1/
20
02
13
/0
1/
20
02
6/
01
/2
00
2
30
/1
2/
20
01
23
/1
2/
20
01
16
/1
2/
20
01
2/
12
/2
00
1
9/
12
/2
00
1
0
Figure 5.3: Butyrate activities in µM substrate/L/h at sites 1 to 4 on the Mitta Mitta River and site 5
on Snowy Creek (reference site) on the nine sample dates from December 2001 to February 2002
(mean ± SD, n=4).
4
Leucine
site1
site2
site4
site5
site3
3.5
uM substrate/L/h
3
2.5
2
1.5
1
0.5
02
/2
00
2
20
02
10
/
02
/
3/
27
/
01
/2
00
2
00
2
20
/
01
/2
00
2
01
/2
13
/
20
02
01
/
6/
30
/
12
/2
00
1
00
1
23
/
12
/2
00
1
12
/2
16
/
20
01
12
/
9/
2/
12
/
20
01
0
Figure 5.4: Leucine activities in µM substrate/L/h at sites 1 to 4 on the Mitta Mitta River and site 5
on Snowy Creek (reference site) on the nine sample dates from December 2001 to February 2002
(mean ± SD, n=4).
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
4
Xyloside
site1
site2
site4
site5
site3
3.5
uM substrate/L/h
3
2.5
2
1.5
1
0.5
10
/0
2/
20
02
3/
02
/2
00
2
27
/0
1/
20
02
20
/0
1/
20
02
13
/0
1/
20
02
6/
01
/2
00
2
30
/1
2/
20
01
23
/1
2/
20
01
16
/1
2/
20
01
9/
12
/2
00
1
2/
12
/2
00
1
0
Figure 5.5: Xylosidase activities in µM substrate/L/h at sites 1 to 4 on the Mitta Mitta River and site
5 on Snowy Creek (reference site) on the nine sample dates from December 2001 to February
2002 (mean ± SD, n=4).
5.4
Discussion
The effects of the CRP in the Mitta Mitta River on the sources and utilisation of DOC in
river water by bacterial communities were examined. It was hypothesised that there would
be an overall increase in rates of water column bacterial enzyme activity during peak
discharges of the CRP compared to the reference stream. The results of this study have
shown a general trend of a very short-term, but substantial increase in activity associated
with the peak flows for most carbon substrates that was not evident in any substrate in the
reference river. The release of peak flows of 4800 ML/day on dates 2 and 5 have increased
the rates of microbial productivity for a diverse range of water column bacteria, which in
turn can be expected to increase the biomass of microbial communities available to
successive trophic levels.
Few studies have explored the response of microbial communities to short time scales such
as peak flow events with the majority of studies using the extracellular enzyme technique
identifying seasonal patterns or sources of carbon (Chappell & Goulder 1995; Boschker &
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
Cappenberg 1998; Foreman et al 1998). Short term peaks of enzyme activity similar to
those seen in the Mitta Mitta River during flow peaks were noted by Burns and Ryder
(2001b) who provide an example of rapid, short term (21 days) changes in enzyme activity
associated with the inundation of river sediments. However, rates of peak enzyme activities
in the Mitta Mitta River are at the lower end of those found in other river systems (eg.
Sinsabaugh et al 1997; Findlay et al 1998; Burns & Ryder 2001b) possibly due to limiting
concentrations of inorganic nutrients (Findlay & Sinsabaugh 1999) demonstrated in
Section 4.
The low rates of activity for xylosidase compared to the other enzymes is expected due to
the relatively low abundance of woody debris in the Mitta Mitta River. However, a number
of issues such as the removal and transport leaf litter and woody debris during the first
Release (not studied as part of this contract), timing of natural litterfall and replenishment
of coarse organic debris may all influence the activity rates of xyloside. Therefore, this
enzyme should not be discounted from any future studies in this or similar river systems.
For example, the pulse of leaf litter entering the stream during leaf fall from willows and
poplars that line the banks of the Mitta Mitta River may an important seasonal source of
carbon for microbial production that could be quantified using xylosidase substrates.
Similarly, the high level of variability seen in the butyrate and leucine substrates should
not discount them from future monitoring studies, although it highlights the need for
increased sample replication.
Activities of alpha and beta glucosidase displayed the most consistent response to increases
in flow discharge. These enzymes are responsible for the degradation of carbohydrase
substrates such as those found in cell walls of aquatic plants and green algae. The Mitta
Mitta River contains extensive benthic algal communities that contain large populations of
filamentous green algae (particularly Stigeoclonium and Oedogonium – Section 6). An
increase in water column Chl-a (Section 4) and a decrease in biofilm Chl-a (Section 6)
during peak flows in the Mitta Mitta River suggest that increases in alpha and beta
glucosidase activity may the result the scouring of benthic algae during peak flows. This is
supported by trends of increased protease and fatty acid esterase activity during flood
peaks, enzymes associated with benthic algal communities containing cyanobacteria. An
increase in the activity of carbohydrase enzymes with distance downstream during the third
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
Release suggests these carbon resources originate from along the entire study reach
indicating the physical disturbance of biofilms along the entire study length.
Findlay and Sinsabaugh (1999) demonstrated increased microbial activity following cell
breakage by macroinvertebrate consumers. We hypothesise that the peak flows of 4800
ML/day are sufficient to result in the physical abrasion and damage of algal cells along the
entire study reach leading to an increase in microbial productivity. This hypothesis is
supported by substantial decreases in biofilm net productivity on flood days possibly due
to the increase in heterotrophic microbial activity (Section 6).
5.5
•
Summary of findings
The release of peak flows of 4800 ML/day on dates 2 and 5 resulted in short-term
increases (days) in the rates of microbial productivity along the entire study reach for a
diverse range of water column bacteria. This in turn can be expected to increase the
biomass of microbial communities available to successive trophic levels.
•
Rates of peak enzyme activities in the Mitta Mitta River were at the lower end of rates
found in other river systems possibly due to limiting concentrations of inorganic
nutrients.
•
The lack of data from the first variable flow release makes interpretation of some
enzyme activities, particularly xylosidase (leaf/woody debris) very difficult, as
potential carbon sources may have been affected by the first variable flow release.
•
Activities of alpha and beta glucosidase displayed the most consistent response to
flooding. These enzymes are responsible for the degradation of carbohydrase substrates
such as those found in cell walls of aquatic plants and green algae.
•
We hypothesise that consistent increases in enzyme activity during peak flows are the
result of the physical abrasion and damage to biofilm algal cells, particularly
filamentous green algae, leading to an increase in microbial productivity.
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
6.0 BIOFILM STRUCTURE AND FUNCTION
6.1
Introduction
Submerged surfaces in lakes and rivers are colonised by assemblages of algae, fungi and
bacteria in a mucilaginous matrix of algal and bacterial exudates and detritus (Wetzel
1983). These are the biofilms (or periphyton) that cover rocks, wood, sediment particles
and other surfaces in aquatic systems. Biofilms form a key level in aquatic ecosystems, and
are a major instream source of carbon in river systems, often making a greater contribution
to biomass and metabolic activity than phytoplankton and macrophytes (Bott 1983). These
organisms are central to important nutrient and biogeochemical processes, and as such may
respond to disturbance before effects on higher organisms are detected. This is because the
higher organisms depend on processes mediated by algal and microbial communities.
Consequently, they form the base of food webs supporting zooplankton, grazers such as
crustaceans, insects, molluscs and some fish (Lock et al. 1984; Rounick & Winterbourn
1986; Stevenson 1996).
Biofilms are assemblages that contain both autotrophic and heterotrophic microorganisms.
The composition and productivity of biofilms are the consequence of multiple interactions
between hydrological, chemical and biotic factors. Processes that control resources
ultimately affect biomass accumulation, with disturbances leading to losses (Biggs 1996).
Succession of biofilms is driven by differential species performance in dispersal, survival
and reproduction; through factors such as resource availability, ecophysiology, life history
and disturbance (Pickett & McDonnell 1989). Nutrients, light and available substrata form
the basic resources for biofilms. These can be modified by external factors, which
ultimately regulate local resource availability. Physical disturbances, such as flow and
changes in water level, act as resource modulators for biofilms through changes to nutrient
and light availability, and by clearing substrata through scouring and abrasion. Principally,
flow regulates accrual of biofilm biomass in river systems through scour, substratum loss
and by increasing light attenuation through higher loads of suspended material. The
scouring of biofilms can lead to changes in the community composition of algal species
within the biofilm by favouring species that can tolerate high velocities (such as diatoms).
Changes to the species composition and biomass of algal biofilms can impact on their
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
ecosystem function, by either reducing or increasing oxygen production dependant on
species present.
The short generation time, sessile nature, responsiveness to environmental condition and
the availability of sound, quantitative methodologies make biofilms ideally suited as
indicators of disturbance in aquatic systems. Information can be collected, processed and
analysed at time scales relevant to both scientific and management interests. Measures of
the structural characteristics of biofilms can be obtained rapidly and at low cost through
measurements such as biomass or taxonomic composition. The determination of biofilm
function can be achieved through measuring changes in system state using techniques such
as biofilm metabolism and extracellular enzyme activity. Functional measures can be used
to integrate diverse communities into a few attributes, allowing easier comparison among
different systems and within systems over time (Pratt & Cairns 1996). The combination of
structural and functional information from biofilms at population, community and
ecosystem levels offers even greater potential for ecologically meaningful analysis (Hart et
al. 1996; Veal et al. 1998).
The aim of this section is to examine the response of structural and functional attributes of
biofilms attached to cobble substrata to variable flow releases in the Mitta Mitta River,
Victoria from December 2001 to February 2002. The following predictions can be made:
1. Decrease in the total and algal biomass, and an increase in the organic biomass of
permanently inundated biofilms in the Mitta Mitta River resulting from peak flow
releases.
2. Change in the relative proportion of algal species of permanently inundated
biofilms in the Mitta Mitta River resulting from peak flow releases.
3. Decrease in the net primary productivity of permanently inundated biofilms in
the Mitta Mitta River from peak flow releases.
4. Variable release patterns associated with the CRP will result in the creation of
new cobble habitat, and these habitats will have biofilms that are structurally and
functionally distinct from permanently inundated cobbles in the Mitta Mitta
River.
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
6.2
Methods
6.2.1 Biofilm Structural Components
Total, organic and algal biomass
Biofilms were collected from cobble that remained permanently inundated throughout the
study on each sampling date and from all sites. Biofilms were also collected from newly
inundated cobble at sites 1 to 4 on dates 2, 3, 5 and 6. On each sampling occasion, 5
cobbles (ranging between 12 and 25cm diameter) were randomly selected from each
relevant habitat at each site, placed in labelled sealed plastic bags and stored on ice in the
dark. Markers were placed at each site to delineate the permanently inundated zone and
cobbles taken from 0.5 to 1.0m from this edge. Newly inundated cobble were taken from
within 0.5m of the water/land boundary on relevant days. Replication and cobble size were
based on the results of Watts et al. (2001).
In the laboratory, the biofilm was scrubbed from each cobble within 48 hours of field
collection into 100 to 500ml of distilled water (dependant on cobble size) using a soft
toothbrush. The volume of water was recorded for individual cobbles. The slurry
containing the scrubbed biofilm was thoroughly homogenised using a household blender
and sub-samples removed for determination of Chl-a (30ml filtered through a GFF 0.75µm
filter) and taxonomic composition (10ml stored in Lugol’s solution). The remaining
solution was placed in an evaporation dish for analysis of organic and inorganic biomass.
Each biomass sample was dried at 80°C for 48 hours, weighed, combusted for 4h at 550°C,
then reweighed. All samples were weighed to four decimal places and converted to dry
weight (DW) and ash free dry weight (AFDW). Chl-a was determined following Tett et al.
(1975). Samples were placed in 10mL methanol containing 150mg MgCO3 to prevent
premature acidification, extracted for 18h at 4°C, transferred to a 70°C water bath and
boiled for 2 minutes. Samples were centrifuged at 4500rpm for 5 minutes and optical
densities at 750 and 666nm were measured pre- and post-acidification (2N HCl) using a
Shimadzu UV/Visible Spectrophotometer.
Each cobble was measured for colonisable rock surface area (CRSA) by covering the
exposed surface area of the rock (excluding the buried surface) with aluminium foil (after
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
Doeg & Lake 1981). CRSA measurements were used to standardise biofilm dry weight
(DW) and ash free dry weight (AFDW) to g/m2 and Chl-a to mg/m2. Percent organic
matter was calculated as the proportion of AFDW to DW and converted to a percentage to
standardise across sites and dates.
6.2.2 Biofilm Taxonomy
Taxonomic composition of the algae was estimated by calculating the biovolume of the
first 750 cells counted by light microscopy at 400x magnification of two replicate biofilm
samples from sites 1 and 4 for all dates and habitats (newly and permanently inundated).
Replication was limited due to the high costs associated with algal taxonomic
identification. The cell dimensions and approximated geometric shape of each taxon were
recorded and used to calculate the biovolumes using the biovol program (Kirschtel 1999).
Biovolume provides a more accurate estimate of relative abundance than cell number as it
standardises results by cell size and removes complications associated with species such as
filamentous Cyanobacteria which do not have individual cells.
Taxonomy was confirmed at 1000x magnification for some specimens. Biovolume of each
taxon was converted to a relative percentage of the total biovolume. Relative biovolume
gives a good assessment of broad taxonomic shifts in biomass. The algae were grouped by
division into Chlorophyta (green algae), Cyanophyta (cyanobacteria) and Bacillariophyta
(diatoms). The algal cells were mainly identified to genus. Species were named where
sufficient detail was available from microscopy, and keys were available for the genus.
6.2.3 Biofilm metabolism
Biofilm metabolism was measured at sites 1 and 4 from permanently inundated cobble on
dates 1 to 9 and from newly inundated cobble on dates 2, 3, 5 and 6. Rates of
photosynthesis and dark respiration of cobble biofilm and of the water column were
measured by monitoring changes in oxygen concentrations within closed chambers using
separate light and dark incubations. Eight dome shaped chambers (4 dark, 4 light)
constructed from clear or opaque perspex with a 50 cm inner diameter were used. The
chambers were mounted in a mobile trailer that could be located immediately adjacent to
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
the river channel (Figure 6.1). For each incubation, a high volume pump mounted on the
trailer filled the trailer body and chambers with river water. Once filled, one or two large
cobble (20-30cm diameter) were placed in each chamber and the chambers sealed to the
base of the trailer to isolate them from the water in the trailer. Water was recirculated
within each chamber using a Whale 911 recirculating pump (max 30L/hour) with inlet and
outlet valves located at the top and bottom of the chamber respectively (Figure 6.2). The
water in the trailer was continuously replaced with new river water to reduce changes in
water temperature during the incubations.
Plate 6.1: Chambers mounted in the mobile trailer used to measure biofilm metabolism.
A port with a rubber o-ring in each chamber fitted the probe from an Orion 835A oxygen
logger, which recorded oxygen concentrations at 10 minute intervals. Each DO probe was
calibrated immediately before each incubation. Incubations were for 3 hours during peak
irradiance between 10am – 4pm on each sample date. Water column metabolism was
assessed by measuring change in DO concentrations over time inside smaller (4L) sealed
light and dark perspex chambers with no cobble inside.
At the end of each incubation the cobble in each chamber was removed and sealed in a
plastic bag for determination of total, organic and algal biomass and CRSA as outlined
above. Logged DO data were downloaded into the Orion Paraly SW105 software package.
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
Net primary production (NPP), Gross Primary Productivity (GPP) and Respiration (R)
were determined by calculating the rate of change in DO concentration within each
chamber over the incubation period using the regression function of Statistica (Statistica
1995). Only R2 values above 0.6 were used in subsequent calculations. All NPP,
GPP and R data were standardised to mgO2/m2/hour.
Oxygen probe
Recirculating
pump
Plate 6.2: One transparent metabolism chamber mounted in the mobile trailer showing location of
oxygen probe and recirculating pump.
6.2.4 Data Manipulation and Analysis
Statistical analyses for biofilm DW, AFDW, organic percent and Chl-a employed single
factor ANOVAs for selected sample dates based on a priori planned comparisons of dates
and habitats. Biofilm DW, AFDW and Chl-a data were square root transformed and
organic percent data were arcsine transformed to remove dependencies between means and
variance. The following planned comparisons were undertaken:
Date 1 (end of first variable flow release) to date 4 (end of second variable flow release)
and date 1 (end of first variable flow release) to date 7 (end of third variable flow release 3)
for each of the five sites to examine the individual and cumulative effects of 2 and 3
variable flow releases.
Newly inundated cobble to permanently inundated cobble at sites 1 to 4 for each of dates 2
(flow peak of the second variable flow release), date 3 (day 8 of the second variable flow
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
release), date 5 (flow peak of the third variable flow release) and date 6 (day 8 of third
variable flow release). Date 7 (end of third variable flow release and start of constant flow
period) to date 9 (end of constant flow period) to examine the effect of extended periods of
constant flows.
The low number of replicates examined for taxonomic composition of algal species
associated with biofilms limited the statistical analysis. Data are presented as relative
percentage of the total biovolume for Chlorophyta (green algae), Cyanophyta
(cyanobacteria) and Bacillariophyta (diatoms) for permanently and newly inundated cobble
habitats from sites 1 and 4.
No statistical analyses were conducted on metabolism data. To maximise the sites and
habitats sampled, separate light and dark incubations were used to estimate GPP and R.
This meant that GPP and R were not calculated for the same cobble, and therefore one
NPP estimate was derived from the mean value of GPP and R for a particular treatment.
6.3
Results
6.3.1 Biofilm total, organic and algal biomass
The dry weight and ash free dry weight of permanently inundated biofilms was highly
variable at all sites on the Mitta Mitta River throughout the CRP and constant flow periods
and were generally less than 100 g/m2 (Figure 6.1) and 10 g/m2 respectively (Figure 6.2).
Biofilms at site 4 were the exception with a dry weight ranging from approximately 100 to
225 g/m2, and an ash weight ranging from approximately 5 to 15 g/m2 during the CRP.
Biofilm dry and ash weight in Snowy Creek were less than those in the Mitta Mitta River,
consistently below 20 g/m2 and 5 g/m2 respectively. Dry and ash weights decreased
following 2 and 3 variable flow releases at all sites. Dry and ash weights increased at all
sites during the period of constant flows following the end of the CRP.
The organic matter percent of biofilms ranged between 5 and 15% at all sites on the Mitta
Mitta River during the CRP (Figure 6.3). An increase in biofilm organic matter percent as
a result of 2 or 3 variable flow releases was only evident at site 1, with little difference
between dates at the other sites. Biofilm organic percent at sites 1 and 2 was more variable
during the period of constant flows following the end of the CRP. Biofilm organic matter
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
percent was highest and most variable at Snowy Creek ranging from around 6 to 29%
throughout the study period.
Similar to the other biomass estimates, the concentrations of Chl-a in permanently
inundated biofilms in the Mitta Mitta River were highly variable, ranging from around 180
mg/m2 to over 1700 mg/m2 throughout the study (Figure 6.4). A trend of decreasing
biofilm Chl-a following 2 or 3 variable flow releases was consistently evident at sites 1, 2
and 4, however, the Chl-a concentration of biofilms increased at site 3 throughout the
CRP. An increase of biofilm Chl-a was seen at all sites during the period of constant flows
following the end of the CRP, with sites 2 and 3 showing a 5 fold increase in this period.
In general, biofilm attributes in the newly inundated cobble habitat were different to those
in the permanently inundated cobbles. Biofilm dry weight in newly inundated cobble was
generally higher that in the permanently inundated cobble (Figures 6.1). The ash free dry
weight of biofilms was generally similar in both habitats throughout the study. The organic
matter percent of biofilms in the permanently inundated habitat was similar to that in the
newly inundated habitat in sites 2 and 3, but generally higher in the newly inundated
cobble at sites 1 and 4. Biofilm Chl-a concentrations were consistently lower in the newly
inundated cobble habitat throughout the study.
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
59
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
3/01/2002
4/01/2002
5/01/2002
6/01/2002
7/01/2002
8/01/2002
9/01/2002
10/01/2002
11/01/2002
12/01/2002
13/01/2002
14/01/2002
15/01/2002
16/01/2002
17/01/2002
18/01/2002
19/01/2002
20/01/2002
21/01/2002
22/01/2002
23/01/2002
24/01/2002
25/01/2002
26/01/2002
27/01/2002
28/01/2002
29/01/2002
30/01/2002
31/01/2002
1/02/2002
2/02/2002
3/02/2002
02
2/01/2002
/2
0
1/01/2002
/0
2
31/12/2001
10
30/12/2001
02
29/12/2001
/2
0
28/12/2001
3/
02
27/12/2001
02
26/12/2001
/2
0
Site 1
/0
1
g/m2
200
27
25/12/2001
02
24/12/2001
/2
0
23/12/2001
/0
1
22/12/2001
02
21/12/2001
20
20/12/2001
/2
0
19/12/2001
/0
1
18/12/2001
02
17/12/2001
13
16/12/2001
/2
0
15/12/2001
01
14/12/2001
6/
01
13/12/2001
/2
0
12/12/2001
/1
2
11/12/2001
01
10/12/2001
30
9/12/2001
/2
0
8/12/2001
/1
2
7/12/2001
23
6/12/2001
01
2
g/m
5/12/2001
/2
0
2/
12
/2
4/ 00
12 1
/2
6/ 00
12 1
/2
8/ 00
12 1
10 /20
/1 0 1
2
12 /20
/1 01
2
14 /20
/1 01
2
16 /20
/1 01
2
18 /20
/1 01
2
20 /20
/1 01
2
22 /20
/1 01
2
24 /20
/1 01
2
26 /20
/1 01
2
28 /20
/1 01
2
30 /20
/1 01
2/
2
1/ 00
01 1
/2
3/ 00
01 2
/2
5/ 00
01 2
/2
7/ 00
01 2
/2
9/ 00
01 2
11 /20
/0 0 2
1
13 /20
/0 02
1
15 /20
/0 02
1
17 /20
/0 02
1
19 /20
/0 02
1
21 /20
/0 02
1
23 /20
/0 02
1
25 /20
/0 02
1
27 /20
/0 02
1
29 /20
/0 02
1
31 /20
/0 02
1/
2
2/ 00
02 2
/2
4/ 00
02 2
/2
6/ 00
02 2
/2
8/ 00
02 2
10 /20
/0 0 2
2/
20
02
4/12/2001
/1
2
01
2/
12
/2
4/ 00
12 1
/2
6/ 00
12 1
/2
8/ 00
12 1
10 /20
/1 01
2
12 /20
/1 01
2
14 /20
/1 01
2
16 /20
/1 01
2
18 /20
/1 01
2
20 /20
/1 01
2
22 /20
/1 01
2
24 /20
/1 01
2
26 /20
/1 01
2
28 /20
/1 01
2
30 /20
/1 01
2/
2
1/ 00
01 1
/2
3/ 00
01 2
/2
5/ 00
01 2
/2
7/ 00
01 2
/2
9/ 00
01 2
11 /20
/0 02
1
13 /20
/0 02
1
15 /20
/0 02
1
17 /20
/0 02
1
19 /20
/0 02
1
21 /20
/0 02
1
23 /20
/0 02
1
25 /20
/0 02
1
27 /20
/0 02
1
29 /20
/0 02
1
31 /20
/0 02
1/
2
2/ 00
02 2
/2
4/ 00
02 2
/2
6/ 00
02 2
/2
8/ 00
02 2
10 /20
/0 02
2/
20
02
g/m2
3/12/2001
16
01
2/
12
/2
4/ 00
12 1
/2
6/ 00
12 1
/2
8/ 00
12 1
10 /20
/1 01
2
12 /20
/1 01
2
14 /20
/1 01
2
16 /20
/1 01
2
18 /20
/1 01
2
20 /20
/1 01
2
22 /20
/1 01
2
24 /20
/1 01
2
26 /20
/1 01
2
28 /20
/1 01
2
30 /20
/1 01
2/
2
1/ 00
01 1
/2
3/ 00
01 2
/2
5/ 00
01 2
/2
7/ 00
01 2
/2
9/ 00
01 2
11 /20
/0 02
1
13 /20
/0 02
1
15 /20
/0 02
1
17 /20
/0 02
1
19 /20
/0 02
1
21 /20
/0 02
1
23 /20
/0 02
1
25 /20
/0 02
1
27 /20
/0 02
1
29 /20
/0 02
1
31 /20
/0 02
1/
2
2/ 00
02 2
/2
4/ 00
02 2
/2
6/ 00
02 2
/2
8/ 00
02 2
10 /20
/0 02
2/
20
02
g/m2
2/12/2001
/2
0
/2
0
g/m2
0
9/
12
2/
12
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
250
Newly inundated
Permanently inundated
150
100
50
4/02/2002
5/02/2002
6/02/2002
7/02/2002
8/02/2002
9/02/2002
10/02/2002
11/02/2002
250
200
Site 2
150
100
50
0
250
200
Site 3
150
100
50
0
250
200
Site 4
150
100
50
0
250
200
Site 5
150
100
50
0
Figure 6.1: Biofilm dry weight in permanently inundated and newly inundated cobble habitats at
sites 1 to 4 on the Mitta Mitta River and site 5 on Snowy Creek (reference site) on the nine sample
dates
from
December
2001
to
February
2002
(mean
±
SD,
n=5).
60
8/12/2001
9/12/2001
10/12/2001
11/12/2001
12/12/2001
13/12/2001
14/12/2001
15/12/2001
16/12/2001
17/12/2001
18/12/2001
19/12/2001
20/12/2001
21/12/2001
22/12/2001
23/12/2001
24/12/2001
25/12/2001
26/12/2001
27/12/2001
28/12/2001
29/12/2001
30/12/2001
31/12/2001
1/01/2002
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
2/01/2002
3/01/2002
4/01/2002
5/01/2002
6/01/2002
7/01/2002
8/01/2002
9/01/2002
10/01/2002
11/01/2002
12/01/2002
13/01/2002
14/01/2002
15/01/2002
16/01/2002
17/01/2002
18/01/2002
19/01/2002
20/01/2002
21/01/2002
22/01/2002
23/01/2002
24/01/2002
25/01/2002
26/01/2002
27/01/2002
28/01/2002
29/01/2002
30/01/2002
31/01/2002
1/02/2002
2/02/2002
10
/0
2/
20
02
15
20
02
g/m2
Site 1
3/
02
/
7/12/2001
27
/0
1/
20
02
g/m2
6/12/2001
13
/0
1/
20
02
20
/0
1/
20
02
12
/
4/ 200
12 1
/
6/ 200
12 1
/
8/ 200
12 1
10 /20
/1 0 1
2
12 /20
/1 0 1
2
14 /20
/1 0 1
2
16 /20
/1 0 1
2
18 /20
/1 0 1
2
20 /20
/1 0 1
2
22 /20
/1 01
2
24 /20
/1 01
2
26 /20
/1 01
2
28 /20
/1 01
2
30 /20
/1 01
2/
1/ 200
01 1
/
3/ 200
01 2
/
5/ 200
01 2
/
7/ 200
01 2
/
9/ 200
01 2
11 /20
/0 0 2
1
13 /20
/0 02
1
15 /20
/0 0 2
1
1 7 /20
/0 0 2
1
1 9 /20
/0 0 2
1
2 1 /20
/0 0 2
1
2 3 /20
/0 0 2
1
2 5 /20
/0 02
1
2 7 /2 0
/0 02
1
2 9 /2 0
/0 02
1
3 1 /2 0
/0 02
1/
2/ 200
02 2
/
4/ 200
02 2
/
6/ 200
02 2
/
8/ 200
02 2
10 /20
/0 0 2
2/
20
02
2/
5/12/2001
20
02
2
20
6/
01
/
g/m
4/12/2001
30
/1
2/
20
01
2/
4/ 200
12 1
/
6/ 200
12 1
/
8/ 200
12 1
10 /20
/1 01
2
12 /20
/1 01
2
14 /20
/1 01
2
16 /20
/1 01
2
18 /20
/1 01
2
20 /20
/1 01
2
22 /20
/1 01
2
24 /20
/1 01
2
26 /20
/1 01
2
28 /20
/1 01
2
30 /20
/1 01
2/
1/ 200
01 1
/
3/ 200
01 2
/
5/ 200
01 2
/
7/ 200
01 2
/
9/ 200
01 2
11 /20
/0 02
1
13 /20
/0 02
1
15 /20
/0 02
1
17 /20
/0 02
1
19 /20
/0 02
1
21 /20
/0 02
1
23 /20
/0 02
1
25 /20
/0 02
1
27 /20
/0 02
1
29 /20
/0 02
1
31 /20
/0 02
1/
2/ 200
02 2
/
4/ 200
02 2
/
6/ 200
02 2
/
8/ 200
02 2
10 /20
/0 02
2/
20
02
2/
1
3/12/2001
16
/1
2/
20
01
23
/1
2/
20
01
2/
4/ 200
12 1
/
6/ 200
12 1
/
8/ 200
12 1
10 /20
/1 01
2
1 2 /2 0
/1 0 1
2
1 4 /2 0
/1 0 1
2
1 6 /2 0
/1 0 1
2
1 8 /2 0
/1 01
2
2 0 /2 0
/1 01
2
2 2 /2 0
/1 0 1
2
2 4 /2 0
/1 0 1
2
2 6 /2 0
/1 0 1
2
2 8 /2 0
/1 0 1
2
3 0 /2 0
/1 01
2/
1/ 200
01 1
/
3/ 200
01 2
/
5/ 200
01 2
/
7/ 200
01 2
/
9/ 200
01 2
11 /20
/0 02
1
13 /20
/0 02
1
15 /20
/0 02
1
1 7 /2 0
/0 02
1
1 9 /2 0
/0 02
1
2 1 /2 0
/0 02
1
2 3 /2 0
/0 02
1
25 /20
/0 02
1
27 /20
/0 02
1
29 /20
/0 02
1
31 /20
/0 02
1/
2/ 200
02 2
/
4/ 200
02 2
/
6/ 200
02 2
/
8/ 200
02 2
10 /20
/0 02
2/
20
02
2/
1
2
g/m
2/12/2001
20
01
20
01
g/m2
0
9/
12
/
2/
12
/
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
25
Newly inundated
Permanently inundated
10
5
3/02/2002
4/02/2002
5/02/2002
6/02/2002
7/02/2002
8/02/2002
9/02/2002
10/02/2002
11/02/2002
25
20
Site 2
15
10
5
0
25
20
Site 3
15
10
5
0
25
Site 4
20
15
10
5
0
25
20
Site 5
15
10
5
0
Figure 6.2: Biofilm ash free dry weight in permanently inundated and newly inundated cobble
habitats at sites 1 to 4 on the Mitta Mitta River and site 5 on Snowy Creek (reference site) on the
nine sample dates from December 2001 to February 2002 (mean ± SD, n=5).
61
7/12/2001
8/12/2001
9/12/2001
10/12/2001
11/12/2001
12/12/2001
13/12/2001
14/12/2001
15/12/2001
16/12/2001
17/12/2001
18/12/2001
19/12/2001
20/12/2001
21/12/2001
22/12/2001
23/12/2001
24/12/2001
25/12/2001
26/12/2001
27/12/2001
28/12/2001
30
30
30
30
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
29/12/2001
30/12/2001
31/12/2001
1/01/2002
2/01/2002
3/01/2002
4/01/2002
5/01/2002
6/01/2002
7/01/2002
8/01/2002
9/01/2002
10/01/2002
11/01/2002
12/01/2002
13/01/2002
14/01/2002
15/01/2002
16/01/2002
17/01/2002
18/01/2002
19/01/2002
20/01/2002
21/01/2002
22/01/2002
23/01/2002
24/01/2002
25/01/2002
26/01/2002
27/01/2002
28/01/2002
29/01/2002
30/01/2002
31/01/2002
1/02/2002
2/02/2002
3/02/2002
10
/0
2/
20
02
Site 1
3/
02
/2
00
2
Organic Matter %
30
27
/0
1/
20
02
Organic Matter %
6/12/2001
20
/0
1/
20
02
2/
2
4/ 001
12
/2
6/ 001
12
/2
8/ 001
12
/
10 200
/1
1
2/
12 200
/1
1
2/
2
14
0
/1 01
2/
16 200
/1
1
2/
18 200
/1
1
2/
20 200
/1
1
2/
22 200
/1
1
2/
24 200
/1
1
2/
26 200
/1
1
2/
2
28
0
/1 01
2/
30 200
/1
1
2/
2
1/ 001
01
/2
3/ 002
01
/2
5/ 002
01
/2
7/ 002
01
/2
9/ 002
01
/
11 200
/0
2
1/
13 200
/0
2
1/
2
15
0
/0 02
1/
17 200
/0
2
1/
19 200
/0
2
1/
21 200
/0
2
1/
23 200
/0
2
1/
2
25
0
/0 02
1/
27 200
/0
2
1/
29 200
/0
2
1/
31 200
/0
2
1/
2
2/ 002
02
/2
4/ 002
02
/2
6/ 002
02
/2
8/ 002
02
/
10 200
/0
2
2/
20
02
2/
1
35
13
/0
1/
20
02
Organic Matter %
5/12/2001
6/
01
/2
00
2
2/
2
4/ 001
12
/2
6/ 001
12
/2
8/ 001
12
/
10 200
/1
1
2/
12 200
/1
1
2/
14 200
/1
1
2/
16 200
/1
1
2/
18 200
/1
1
2/
2
20
0
/1 01
2/
22 200
/1
1
2/
24 200
/1
1
2/
26 200
/1
1
2/
2
28
0
/1 01
2/
30 200
/1
1
2/
2
1/ 001
01
/2
3/ 002
01
/2
5/ 002
01
/2
7/ 002
01
/2
9/ 002
01
/
11 200
/0
2
1/
13 200
/0
2
1/
15 200
/0
2
1/
17 200
/0
2
1/
19 200
/0
2
1/
2
21
0
/0 02
1/
23 200
/0
2
1/
25 200
/0
2
1/
27 200
/0
2
1/
2
29
0
/0 02
1/
31 200
/0
2
1/
2
2/ 002
02
/2
4/ 002
02
/2
6/ 002
02
/2
8/ 002
02
/
10 200
/0
2
2/
20
02
2/
1
4/12/2001
30
/1
2/
20
01
Organic Matter %
3/12/2001
23
/1
2/
20
01
2/
2
4/ 001
12
/2
6/ 001
12
/2
8/ 001
12
/
10 200
/1
1
2/
12 200
/1
1
2/
14 200
/1
1
2/
2
16
0
/1 0 1
2/
18 200
/1
1
2/
20 200
/1
1
2/
22 200
/1
1
2/
24 200
/1
1
2/
26 200
/1
1
2/
28 200
/1
1
2/
2
30
0
/1 0 1
2/
2
1/ 001
01
/2
3/ 002
01
/2
5/ 002
01
/2
7/ 002
01
/2
9/ 002
01
/
11 200
/0
2
1/
13 200
/0
2
1/
15 200
/0
2
1/
17 200
/0
2
1/
19 200
/0
2
1/
21 200
/0
2
1/
2
23
0
/0 0 2
1/
25 200
/0
2
1/
27 200
/0
2
1/
29 200
/0
2
1/
31 200
/0
2
1/
20
2/
0
02 2
/2
4/ 002
02
/2
6/ 002
02
/2
8/ 002
02
/
10 200
/0
2
2/
20
02
2/
1
2/12/2001
16
/1
2/
20
01
Organic Matter %
0
9/
12
/2
00
1
2/
12
/2
00
1
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
Newly inundated
Permanently inundated
25
20
15
10
5
4/02/2002
5/02/2002
6/02/2002
7/02/2002
8/02/2002
9/02/2002
10/02/2002
11/02/2002
35
Site 2
25
20
15
10
5
0
35
Site 3
25
20
15
10
5
0
35
Site 4
25
20
15
10
5
0
35
Site 5
25
20
15
10
5
0
Figure 6.3: Biofilm organic matter percent in permanently inundated and newly inundated cobble
habitats at sites 1 to 4 on the Mitta Mitta River and site 5 on Snowy Creek (reference site) on the
nine sample dates from December 2001 to February 2002 (mean ± SD, n=5).
62
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
Comparison of the effect of two variable flow releases and three variable flow releases on
biofilm biomass in permanently inundated cobble habitat.
Significant reductions in the dry weight and ash free dry weight of permanently inundated
biofilm were evident at all sites on the Mitta Mitta River of biofilm biomass by the end of
the third variable flow release (date 7) compared the end of the first variable flow release
(date 1). This occurred over a period of time when there was no significant change in dry
and ash weights at the reference site (site 5 Snowy Creek) (Table 6.1, Figures 6.1, 6.2). A
comparison of only 2 variable flow releases (dates 1 and 4) shows evidence of loss of
biomass but not consistently across all sites (Table 6.1). A significant decrease in biofilm
dry weight was found at sites 1, 2 and 4, with ash weights significantly different between
dates 1 and 4 only at sites 2 and 3 in the Mitta Mitta River. There was also a significant
difference between dates 1 and 4 at the reference site (site 5 Snowy Creek) for biofilm ash
free dry weight.
The organic matter percent of permanently inundated biofilms did not display any
consistent trends between sites or sample dates. A significant increase in organic percent
was only evident at site 1 at the end of both the second and third variable flow release
(dates 4 and 7) (Table 6.1, Figure 6.3). This trend was also apparent at Snowy Creek (site
5).
A significant reduction in biofilm Chl-a concentration on permanently inundated cobble
was found only at site 2 at the end of the third variable flow release (Table 6.1, Figure 6.4).
Conversely, the Chl-a concentration of biofilms at site 3 increased significantly following
the end of both the second and third variable flow releases.
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
63
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
10
/0
2/
20
02
2
12
2000
Site 5
4/
/2
0
12 01
/2
6/ 00
12 1
/2
8/ 00
12 1
10 /20
/1 01
2
12 /20
/1 01
2
14 /20
/1 01
2
16 /20
/1 01
2
18 /20
/1 01
2
20 /20
/1 01
2
22 /20
/1 01
2
24 /20
/1 01
2
26 /20
/1 01
2
28 /20
/1 01
2
30 /20
/1 01
2/
2
1/ 00
01 1
/2
3/ 00
01 2
/2
5/ 00
01 2
/2
7/ 00
01 2
/2
9/ 00
01 2
11 /20
/0 02
1
13 /20
/0 0 2
1
15 /20
/0 0 2
1
17 /20
/0 0 2
1
19 /20
/0 0 2
1
21 /20
/0 0 2
1
23 /20
/0 0 2
1
25 /20
/0 0 2
1
27 /20
/0 0 2
1
29 /20
/0 0 2
1
31 /20
/0 0 2
1/
2
2/ 00
02 2
/2
4/ 00
02 2
/2
6/ 00
02 2
/2
8/ 00
02 2
10 /20
/0 02
2/
20
02
2/
mg/m2
2/
12
/2
00
1
4/
12
/2
00
1
6/
12
/2
00
1
8/
12
/2
00
1
10
/1
2/
20
01
12
/1
2/
20
01
14
/1
2/
20
01
16
/1
2/
20
01
18
/1
2/
20
01
20
/1
2/
20
01
22
/1
2/
20
01
24
/1
2/
20
01
26
/1
2/
20
01
28
/1
2/
20
01
30
/1
2/
20
01
1/
01
/2
00
2
3/
01
/2
00
2
5/
01
/2
00
2
7/
01
/2
00
2
9/
01
/2
00
2
11
/0
1/
20
02
13
/0
1/
20
02
15
/0
1/
20
02
17
/0
1/
20
02
19
/0
1/
20
02
21
/0
1/
20
02
23
/0
1/
20
02
25
/0
1/
20
02
27
/0
1/
20
02
29
/0
1/
20
02
31
/0
1/
20
02
2/
02
/2
00
2
4/
02
/2
00
2
6/
02
/2
00
2
8/
02
/2
00
2
10
/0
2/
20
02
mg/m2
2/
12
/2
00
1
4/
12
/2
00
1
6/
12
/2
00
1
8/
12
/2
00
1
10
/1
2/
20
01
12
/1
2/
20
01
14
/1
2/
20
01
16
/1
2/
20
01
18
/1
2/
20
01
20
/1
2/
20
01
22
/1
2/
20
01
24
/1
2/
20
01
26
/1
2/
20
01
28
/1
2/
20
01
30
/1
2/
20
01
1/
01
/2
00
2
3/
01
/2
00
2
5/
01
/2
00
2
7/
01
/2
00
2
9/
01
/2
00
2
11
/0
1/
20
02
13
/0
1/
20
02
15
/0
1/
20
02
17
/0
1/
20
02
19
/0
1/
20
02
21
/0
1/
20
02
23
/0
1/
20
02
25
/0
1/
20
02
27
/0
1/
20
02
29
/0
1/
20
02
31
/0
1/
20
02
2/
02
/2
00
2
4/
02
/2
00
2
6/
02
/2
00
2
8/
02
/2
00
2
10
/0
2/
20
02
mg/m2
2/
12
/2
00
1
4/
12
/2
00
1
6/
12
/2
00
1
8/
12
/2
00
1
10
/1
2/
20
01
12
/1
2/
20
01
14
/1
2/
20
01
16
/1
2/
20
01
18
/1
2/
20
01
20
/1
2/
20
01
22
/1
2/
20
01
24
/1
2/
20
01
26
/1
2/
20
01
28
/1
2/
20
01
30
/1
2/
20
01
1/
01
/2
00
2
3/
01
/2
00
2
5/
01
/2
00
2
7/
01
/2
00
2
9/
01
/2
00
2
11
/0
1/
20
02
13
/0
1/
20
02
15
/0
1/
20
02
17
/0
1/
20
02
19
/0
1/
20
02
21
/0
1/
20
02
23
/0
1/
20
02
25
/0
1/
20
02
27
/0
1/
20
02
29
/0
1/
20
02
31
/0
1/
20
02
2/
02
/2
00
2
4/
02
/2
00
2
6/
02
/2
00
2
8/
02
/2
00
2
10
/0
2/
20
02
mg/m2
Site 1
3/
02
/2
00
2
mg/m
1600
27
/0
1/
20
02
20
/0
1/
20
02
13
/0
1/
20
02
6/
01
/2
00
2
30
/1
2/
20
01
23
/1
2/
20
01
16
/1
2/
20
01
9/
12
/2
00
1
2/
12
/2
00
1
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
2000
Newly inundated
Permanently inundated
1200
800
400
0
2000
1600
Site 2
1200
800
400
2000
0
1600
Site 3
1200
800
400
0
2000
1600
Site 4
1200
800
400
0
1600
1200
800
400
0
Figure 6.4: Biofilm chlorophyll-a (Chl-a) concentrations in permanently inundated and newly
inundated cobble habitats at sites 1 to 4 on the Mitta Mitta River and site 5 on Snowy Creek
(reference site) on the nine sample dates from December 2001 to February 2002 (mean ± SD,
n=5).
64
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
Table 6.1: Probability value and significance levels of one-way ANOVAs comparing biofilm dry
weight, ash free dry weight, organic matter percent and chlorophyll-a (Chl-a) in permanently
inundated cobble habitats between sample dates 1 and 4 and between dates 1 and 7 at four sites
in the Mitta Mitta River (sites 1 to 4) and in Snowy Creek (site 5). Direction of trend is shown in
brackets. ns = not significant, * = P < 0.05, ** = P < 0.01, *** = P < 0.001.
Dry weight
Ash free dry weight
Date1 to 4
Date 1 to 7
Date1 to 4
Date 1 to 7
Site 1
0.001*** (1>4)
0.001*** (1>7)
0.212
0.001*** (1>7)
Site 2
0.001*** (1>4)
0.001*** (1>7)
0.001*** (1>4)
0.001*** (1>7)
Site 3
0.135
0.001*** (1>7)
0.007** (1>4)
0.001*** (1>7)
Site 4
0.047*
0.001*** (1>7)
0.459
0.001*** (1>7)
Site 5 (ref)
0.097
0.052
0.001*** (1>4)
0.627
(1>4)
Organic matter %
Chlorophyll-a
Date1 to 4
Date 1 to 7
Date1 to 4
Date 1 to 7
Site 1
0.008 ** (1>4)
0.001*** (1<7)
0.132
0.089
Site 2
0.153
0.225
0.421
0.011*
Site 3
0.018* (1<4)
0.772
0.017* (1<4)
0.001*** (1<7)
Site 4
0.077
0.201
0.265
0.651
Site 5 (ref)
0.001*** (1>4)
0.008** (1>7)
0.110
0.009** (1<7)
(1>7)
Sample dates 2 and 3 in variable flow release 2, and dates 5 and 6 in variable flow release
3 show that many of the biofilm biomass attributes are highly variable within an individual
variable flow release. For example, there are clear reductions in the Chl-a concentrations
of biofilms at sites 1 and 2 during the flow peaks of the variable flow releases (dates 2 and
5) (Figure 6.4), indicating that algae are being scoured from cobble during peak flows but
the algal biomass is recovering quickly to pre flow peak levels.
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
65
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
Comparisons of biofilm biomass in permanently inundated and newly inundated cobble
habitat.
Newly inundated cobble had significantly lower biofilm dry weight at all sites only on date
2 (the peak of the second variable flow release) (Table 6.2). The dry weight of newly
inundated biofilms at site 1 continued to increase over time resulting in no significant
difference between the habitats by the last sample date (date 6)(Figure 6.1). Biofilm dry
weight at sites 2 and 3 was highly variable in both habitats resulting in similar weights on
dates 3 and 5. An increase in weight in the permanently inundated habitat and a
corresponding decrease in weight in newly inundated habitats resulted in a significantly
higher biomass in the permanently inundated habitats between dates 5 and 6. Values for
biofilm dry weight in the newly inundated habitat at site 4 were similar to the other sites,
however, significant differences between permanently inundated and newly inundated
habitats were found on all dates as a result much higher weights in the permanently
inundated habitat.
Similar to biofilm dry weight, ash free dry weights were only significantly lower in the
newly inundated habitat at all sites on the first sample date (flow peak of the second
variable flow release) (Table 6.2, Figure 6.2) The ash weight of newly inundated biofilms
at site 1 increased over time with little change in the ash weight of the permanently
inundated biofilms resulting in no significant difference between the habitats by the last
sample date (date 6). Biofilm ash weight at sites 2 and 3 were relatively stable throughout
the study period. Significant differences between the two habitats at these sites, particularly
date 6 resulted from increased in ash weights in the permanently inundated habitat.
Biofilm organic matter percent was similar between the newly and permanently inundated
habitats at sites 1 to 3 on most dates (Figure 6.3). Increased biofilm organic matter percent
in newly inundated habitats on day 8 of each variable flow release (dates 3 and 6) at site 1
resulted in significant differences between habitats on these dates (Table 6.2). Similarly,
increased biofilm organic matter percent in permanently inundated habitats on the flow
peak of each variable flow release (dates 2 and 5) at site 3 resulted in significant
differences between habitats on these dates. The most notable result was the significantly
higher biofilm organic matter percent in the newly inundated cobble at site 4 on all dates.
Biofilm Chl-a concentration was significantly lower on all dates and at all sites (except site
3, date 3) in newly inundated cobble during the CRP (Table 6.2, Figure 6.4). This suggests
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
66
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
that newly inundated cobble were not inundated long enough (with individual or
cumulative inundations) to accumulate the algal biomass found in the permanently
inundated habitats during the CRP.
Table 6.2: Probability value and significance levels of one-way ANOVA comparing biofilm dry
weight, ash free dry weight, organic matter percent and chlorophyll-a (Chl-a) between permanently
inundated (P) and newly inundated (N) cobble habitats at four sites in the Mitta Mitta River on four
sample dates. Direction of trend is shown in brackets. ns = not significant, * = P < 0.05, ** = P <
0.01, *** = P < 0.001.
Date 2
Date3
Date 5
Date 6
Site 1
0.001*** (N<P)
0.001*** (N<P)
0.054
0.052
Site 2
0.001*** (N<P)
0.491
0.113
0.001*** (N<P)
Site 3
0.001*** (N<P)
0.057
0.071
0.013*
Site 4
0.001*** (N<P)
0.001*** (N<P)
0.001*** (N<P)
0.001*** (N<P)
Site 1
0.009** (N<P)
0.055
0.071
0.771
Site 2
0.001*** (N<P)
0.630
0.059
0.001*** (N<P)
Site 3
0.001*** (N<P)
0.001*** (N<P)
0.227
0.013*
(N<P)
Site 4
0.048*
0.573
0.021*
0.045*
(N<P)
(N>P)
Dry Weight
(N<P)
AFDW
(N<P)
(N<P)
Organic %
Site 1
0.143
0.010** (N>P)
0.498
0.014*
Site 2
0.235
0.441
0.460
0.692
Site 3
0.041*
0.096
0.011*
Site 4
0.001*** (N>P)
0.001*** (N>P)
0.001*** (N>P)
0.001*** (N>P)
Site 1
0.001*** (N<P)
0.009** (N<P)
0.001*** (N<P)
0.021*
Site 2
0.001*** (N<P)
0.001*** (N<P)
0.001*** (N<P)
0.001*** (N<P)
Site 3
0.001*** (N<P)
0.059
0.001*** (N<P)
0.001*** (N<P)
Site 4
0.001*** (N<P)
0.004** (N<P)
0.001*** (N<P)
0.001*** (N<P)
(N<P)
(N<P)
0.336
Chlorophyll a
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
(N<P)
67
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
Effect of 37 days of constant and low flows on biofilm biomass in permanently inundated
cobble
The dry weight and ash free dry weight of permanently inundated biofilms were
significantly higher at all sites on the Mitta Mitta River at the end of the constant flows
(date 9) compared to the start of constant flow period (date 7) (Table 6.3). This trend was
most evident at sites 2 and 3 which showed up to a 5 fold increase in weights between
dates 7 and 9 (Figures 6.1, 6.2).
Biofilm organic matter percent on permanently inundated cobble was not significantly
different between dates 7 and 9 (Table 6.1). Date 8, midway into the period of constant
flows shows that biofilm organic matter percent is not stable throughout this period (Figure
6.2). Biofilms at all sites display a trend of reduced organic percent to day 8 and an
increase to date 9 to values similar to those on date 7. Site 5, the reference stream that
received relatively constant flows during this period, displayed the opposite trend, with
organic matter percent decreasing significantly during the same period.
The Chl-a concentration of permanently inundated biofilms increased significantly from
dates 7 to 9 only in sites 2 and 3, (Table 6.3) displaying a 5 fold increase during this
period. Similar to organic percent, biofilms at sites 1 and 4 displayed a trend of reduced
organic percent to day 8 followed by an increase to date 9 to values similar to those on date
7.
Table 6.3: Probability value and significance levels of one-way ANOVAs comparing biofilm dry
weight, ash free dry weight, organic matter percent and chlorophyll-a (Chl-a) between the end of
the cyclic flow release pattern (date 7) to the end of the 37 days constant flows (date 9) in
permanently inundated cobble habitats at four sites in the Mitta Mitta River and in Snowy Creek. ns
= not significant, * = P < 0.05, ** = P < 0.01, *** = P < 0.001.
DW
AFDW
Organic matter %
Chlorophyll a
Date7 to 9
Date7 to 9
Date7 to 9
Date7 to 9
Site 1
0.043*
0.022*
(7<9)
0.061
0.261
Site 2
0.002** (7<9)
0.001*** (7<9)
0.051
0.001*** (7<9)
Site 3
0.001*** (7<9)
0.001*** (7<9)
0.092
0.001*** (7<9)
Site 4
0.007** (7<9)
0.009** (7<9)
0.088
0.519
Site 5 (ref)
0.117
0.338
0.003**
(7<9)
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
(7>9)
0.068
68
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
6.3.2 Biofilm Algal Species Composition
The species richness of benthic algae within biofilms attached to cobble in the Mitta Mitta
River did not vary greatly throughout the study with no trends apparent over time or
between sites. Species richness ranged from 9 to 14 taxon for both habitats at each site
(Table 6.4). There was no obvious shift over time, or between permanently and newly
inundated habitats, in the broad divisions of algae recorded at each site with diatoms
consistently dominating the biofilm species richness. Thirty six species of algae were
found at sites 1 and 4 across the 9 sample dates, 5 species of Chlorophyta (green algae), 4
species of Cyanobacteria (blue-green algae) and 27 species of diatoms. Most species were
present at both sites 1 and 4. Spyrogyra (a filamentous green) was only recorded from site
4 and unicellular green algae were found only at site 1, and 4 species of diatoms were
restricted to only one site.
Table 6.4: Number of species recorded within each algal division in permanently (P) and newly (N)
inundated habitats at sites 1 and 4 on the Mitta Mitta River for sample dates 1 to 9.
Site 1
Sample
date
Site 4
Green
Bluegreen
Diatoms Total
Green
Bluegreen
Diatoms Total
1
2
3
4
5
6
7
8
9
P
P
P
P
P
P
P
P
P
2
2
1
2
2
0
2
2
3
3
2
1
2
2
3
1
2
1
9
9
9
8
6
11
7
9
7
14
13
11
12
10
14
10
13
11
1
2
2
2
2
3
1
0
2
1
2
1
2
1
2
0
2
2
11
8
6
6
8
8
11
12
8
13
12
9
10
11
13
12
14
12
2
3
5
6
N
N
N
N
3
1
0
2
1
1
1
1
9
12
12
6
13
14
13
9
2
1
0
0
1
1
1
1
8
8
12
10
11
10
13
11
Comparison of the effect of two variable flow releases and three variable flow releases on
biofilm species composition in permanently inundated cobble habitat.
There were substantial changes in the relative biovolume of green, blue-green and diatom
algal divisions throughout the CRP at both sites (Figures 6.5, 6.6). The peak of the second
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
69
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
variable flow release (date 2) resulted in the removal of all blue green algae (dominated by
Planktothrix a filamentous blue-green algae, Table 6.5) at site 1 and an increase of 55% in
the relative biovolume of diatoms within the biofilm.
Table 6.5: The percentage contribution of individual algal taxon to total relative biovolume in
permanently (P) and newly (N) inundated habitats at sites 1 and 4 on the Mitta Mitta River for
sample dates 1 to 9.
Chlorophyta
Stigeoclonium Oedogonium
Cyanobacteria
Diatoms
Lyngbya Planktothrix Phormidium Fragillaria Achnanthidium
2.5
Site 1
1
2
3
4
5
6
7
8
9
P
P
P
P
P
P
P
P
P
58.9
42.6
25.5
14.4
40.8
15.6
18.5
12.8
3.6
2
3
5
6
N
N
N
N
51.4
43.8
47.8
72.5
5.8
Site 4
1
2
3
4
5
6
7
8
9
P
P
P
P
P
P
P
P
P
97.2
67.5
84.5
18.5
89.3
16.8
2
3
5
6
N
N
N
N
22.0
53.7
29.0
1.2
4.1
1.9
3.9
12.0
14.1
7.3
16.1
2.1
1.2
0.7
1.3
19.3
3.5
42.2
3.9
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
16.1
58.9
18.8
28.8
25.0
16.4
19.9
23.0
21.6
19.5
20.9
14.4
37.2
12.0
41.8
16.5
11.2
1.7
13.0
4.7
17.3
2.4
25.4
39.4
38.9
0.7
24.4
4.9
14.7
4.4
25.7
6.9
1.9
3.2
27.2
3.1
22.1
18.2
0.8
3.6
7.3
48.9
1.5
56.3
38.1
9.3
36.1
85.2
6.2
11.1
20.8
5.2
7.4
70
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
Site 1
100%
90%
% Relative Biovolume
80%
70%
60%
50%
40%
30%
20%
10%
Chlorophyta
Cyanobacteria
10
/0
2/
20
02
3/
02
/2
00
2
27
/0
1/
20
02
20
/0
1/
20
02
13
/0
1/
20
02
6/
01
/2
00
2
30
/1
2/
20
01
23
/1
2/
20
01
16
/1
2/
20
01
9/
12
/2
00
1
2/
12
/2
00
1
0%
Diatom
Figure 6.5: Cumulative percentage of the relative biovolume of the three major algal divisions
(Chlorophyta, Cyanobacteria and diatoms) recorded on permanently inundated cobble in the Mitta
Mitta River at Site 1.
Site 4
100%
90%
% Relative Biovolume
80%
70%
60%
50%
40%
30%
20%
10%
Chlorophyta
Cyanobacteria
/2
00
2
10
/0
2
3/
02
/2
00
2
/2
00
2
27
/0
1
/2
00
2
20
/0
1
/2
00
2
13
/0
1
6/
01
/2
00
2
/2
00
1
30
/1
2
/2
00
1
23
/1
2
/2
00
1
16
/1
2
9/
12
/2
00
1
2/
12
/2
00
1
0%
Diatom
Figure 6.6: Cumulative percentage of the relative biovolume of the three major algal divisions
(Chlorophyta, Cyanobacteria and diatoms) recorded on permanently inundated cobble in the Mitta
Mitta River at Site 4.
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
However, by the end of the second variable flow release the relative biovolume of green
algae was less than date 1, and the relative biovolume of blue-green algae had increased
from 31.7% to 78.8% and dominated by two filamentous species (Lyngbya and
Planktothrix). The third flow peak (date 5) again saw a reduction in the relative biovolume
of blue greens of approximately 37% and small increases in the other two divisions. At the
end of the third variable flow release (date 7) the biofilms were substantially different to
those at the end of the first variable flow release being dominated by diatoms, particularly
Fragillaria, a very large non colonial species.
The flow peak of the second variable flow release (date 2) did not result in an immediate
shift in algal divisions at site 4 (Figure 6.6), with only a slight decrease in the relative
biovolume of the filamentous branching green algae Stigeoclonium (Table 6.5). However,
by the end of the second variable flow release (date 4) the relative biovolume of green
algae had dropped by approximately 65% and the Stigeoclonium replaced completely by
Oedogonium, with diatom species dominating the biofilm. The third flow peak (date 5)
again saw an increase in the in the relative biovolume of greens (almost entirely
Stigeoclonium ) of approximately 70%. At the end of the third variable flow release (date
7) this species of filamentous algae was again substantially reduced in biovolume. Similar
to site 1, biofilms at site 4 were substantially different to those at the end of the first
variable flow release being dominated by diatoms, particularly Achnanthidium, an early
successional taxon.
Comparisons of biofilm species composition in permanently inundated and newly
inundated cobble habitats.
The wetting of cobble banks as a result of the CRP in the Mitta Mitta River created biofilm
assemblages in newly inundated habitats that were consistently different at the division and
species levels to the biofilms on permanently inundated cobble (Figures 6.7, 6.8). The
relative biovolume of major algal divisions on newly inundated cobble at site 1 are
relatively similar on each date, and therefore differences between habitats are driven by
changes in the permanently inundated biofilms. Biofilms at site 1 in both habitats are most
similar on dates 3 and 5, but an absence of blue-green algae on date 2 and green algae on
date 6 in the permanently inundated habitat result in very different biofilm assemblages
between habitats on these dates. Green algae, specifically Stigeoclonium, dominate the
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
newly inundated biofilms on each date ranging from 43.8% to 73.2% of the total
biovolume. An increase in the relative biovolume of Achnanthidium, an early successional
taxon on dates coinciding with peak flows (dates 2 and 5) has resulted in an increase in the
overall relative biovolume of diatoms on these dates. Differences in the species
contributing to the relative biovolume of blue-green algae between habitats is only evident
on the last date as the permanently inundated biofilms have 3 species of blue-green algae
compared to only 1 species, Lyngbya (a filamentous species), present in the newly
inundated biofilms.
Unlike site 1, differences between habitats in the relative biovolume of the major algal
divisions at site 4 are driven by changes in both permanently and newly inundated biofilms
over time. Newly inundated biofilms have substantially higher biovolumes of diatoms,
dominated by Achnanthidium, than permanently inundated habitats on dates 2, 3 and 5. On
date 6 (day 8 of the third variable flow release), permanently inundated biofilms have a
substantially higher biovolume of Achnanthidium than newly inundated biofilms.
Permanently inundated biofilms consistently have a higher percentage of green algae
(Stigeoclonium) than newly inundated biofilms. On dates 5 and 6 newly inundated biofilms
have no green algae recorded, dominated by 70% diatoms on date 5 and 85% blue greens
(solely Lyngbya) on date 6.
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
P
N
P
N
Site 1
P
N
P
N
100%
90%
% Relative Biovolume
80%
70%
60%
50%
40%
30%
20%
10%
0%
3/12/2001
10/12/2001
Chlorophyta
17/12/2001
Cyanobacteria
24/12/2001
Diatom
Figure 6.7: Cumulative percentage of the relative biovolume of the three major algal divisions
(Chlorophyta, Cyanobacteria and diatoms) recorded on permanently (P) and newly (N) inundated
cobble in the Mitta Mitta River at Site 1.
Site 4
P
N
P
N
P
N
P
N
100%
90%
% Relative Biovolume
80%
70%
60%
50%
40%
30%
20%
10%
0%
3/12/2001
10/12/2001
Chlorophyta
17/12/2001
Cyanobacteria
24/12/2001
Diatom
Figure 6.8: Cumulative percentage of the relative biovolume of the three major algal divisions
(Chlorophyta, Cyanobacteria and diatoms) recorded on permanently (P) and newly (N) inundated
cobble in the Mitta Mitta River at Site 4.
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
Effect of 37 days of constant and low flows on biofilm species composition in permanently
inundated cobble
The extended period of constant flows at the end of the CRP resulted in only a minor
change in algal divisions but larger changes in dominant taxa at site 1. The relative
biovolume of green algae increases by approximately 13% due to an increase in the
biovolume of Oedogonium, a late successional filamentous green algae. Diatom species
(particularly Achnanthidium and Fragillaria) dominate the biofilm biovolume on dates 7
and 9 at approximately 62% and 52% respectively. This dominance is reduced on date 8 by
an increase in the biovolume of blue-green algae, which constitute 46% of the total
biovolume on that date.
The shift in algal composition of biofilms is more dramatic at site 4 where the biofilm
shifts from one dominated by diatoms (57% mainly Achnanthidium and Fragillaria) and
green algae (43% entirely Oedogonium) on date 7 to one with 88% on date 8 and 96% blue
green algae on date 9.
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
6.3.3 Biofilm metabolism
Comparison of the effect of two variable flow releases and three variable flow releases on
biofilm net productivity in permanently inundated cobble habitat.
The net primary productivity of permanently inundated biofilms displayed enormous
variability during the CRP, ranging from 12.82 mgO2/m2/h at site 1 on date 1, to 3.69
mgO2/m2/h at site 1 on date 5 (Figure 6.9). The rates of net productivity of biofilms were
high and similar at both sites following the end of the first variable flow release. Net
primary productivity was reduced by up to one third at both sites to approximately 4
mgO2/m2/h during the peak of the second variable flow release. Response trajectories at
sites 1 and 4 differed after this point. Biofilm metabolism at site 1 increased rapidly to date
4 (end of the second variable flow release), returning to rates similar to those at the end of
the first variable flow release. Conversely, the biofilm metabolism at site 4 increased by
three-fold to date 3 and then fell to approximately 6 mgO2/m2/h by the end of the second
variable flow release. The second variable flow release resulted in less marked changes to
biofilm net productivity with rates on dates 5 and 7 relatively similar at approximately 6
mgO2/m2/h. Rates of biofilm net productivity were substantially lower at the end of the
CRP than at the end of the first variable flow release. Water column net productivity varied
little throughout the CRP consistently less than 2 mgO2/m2/h. Slight increases were noted
during the peaks of each variable flow release.
Comparisons of biofilm net productivity in permanently inundated and newly inundated
cobble habitat.
The net productivity of newly inundated cobble was substantially lower than permanently
inundated cobble at both sites for the first three dates. Newly inundated cobble that had not
been inundated for approximately 14 days (since the previous flow peak) on dates 2 and 5
were net consumers of oxygen. Newly inundated biofilms at site 1 was strongly
heterotrophic with a net productivity of approximately minus 2.5 to 3 mgO2/m2/h. Newly
inundated biofilms at site 4 were less heterotrophic consuming approximately 0.7
mgO2/m2/h on date 2 and displaying low levels of positive net productivity during the third
flow peak. Biofilms on newly inundated cobble that had been inundated for 8 days on date
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
3 were net producers of oxygen but still has much lower rates of productivity than biofilms
on permanently inundated cobble. However, by date 6 (8 days after the third flow peak) net
productivity in the newly inundated cobble was slightly higher than from biofilms that
were permanently inundated. This suggests that cumulative wetting and/or drying periods
stimulate biofilm productivity.
Effect of 37 days of constant flows on biofilm net productivity in permanently inundated
cobble
The extended period of constant flows at the end of the CRP resulted in a rapid decline in
biofilm productivity at both sites. After 37 days constant flows, biofilm net productivity at
site 1 was only slightly higher than in the water column (approximately 2 mgO2/m2/h) and
negative at site 4.
14
newly inundated site 1
12
newly inundated site 4
permanently inundated site 1
10
NPP mg O2/m2/hour
permanently inundated site4
8
water column
6
4
2
2
2
/0
2
/0
/0
10
/0
1
5/
02
2
/0
2
31
/0
1
/0
2
26
21
/0
1
/0
2
/0
16
/0
1
/0
/0
1
11
6/
01
/0
2
2
2
/0
1/
01
1
/0
27
/1
2
/0
/1
2
22
/1
2
/0
1
1
1
17
/1
2
/0
/0
12
-2
7/
12
2/
12
/0
1
1
0
-4
Figure 6.9: Biofilm and water column net primary productivity (mgO2/m2/h) from newly inundated
and permanently inundated habitats at sites 1 and 4 on the Mitta Mitta River.
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
6.4
Discussion.
This study examined the effects of the CRP from Dartmouth Dam to the Mitta Mitta River
on the biomass, species composition and productivity of biofilms attached to cobble
substrata. The implementation of this release pattern resulted in substantial changes to the
structure and function of biofilms through scouring and sloughing of biofilms and the
creation of newly inundated cobble areas through variable discharge volumes. However,
many of the changes associated with the CRP were short lived, with the period of constant
flows following the variable releases resulting in biofilms with a high biomass, a very low
net productivity and dominated by few species of blue-green algae.
The growth and prosperity of biofilms in river systems has been shown to be controlled by
complex interactions between hydrological, water quality and biotic variables including
factors such as flow disturbance, resource supply and grazer control (Biggs 1996).
Resources such as light, relatively low concentrations of organic and inorganic nutrients,
availability of cobble substrata and general water quality were similar across all sites in the
Mitta Mitta River. This suggests that responses of biofilm attributes during and after the
CRP are predominantly the result of changes in either flow variables such as velocity and
variability in water level heights or altered rates of biofilm herbivory (which may also be
flow mediated).
Biofilms were found to respond very rapidly to changes in flow regime. Structural and
functional responses in biofilms were evident immediately following each peak flow, as
well integrating responses to flow regime over longer time periods. The recovery of algal
communities following disturbance can vary from days to months depending on the
duration and frequency of the disturbance (Dodds et al. 1996; Benenati et al. 1998; Biggs
et al. 1999), which may explain the occurrence of significant results across the range of
temporal scales for different biofilm attributes. Biofilms also displayed structural and
functional responses to the wide variety of flow conditions experienced in the Mitta Mitta
River during the study. This finding is consistent with the results of Watts et al. (2001),
who found that there were highly predictable associations between biofilm attributes such
as biomass and net productivity and hydrological variables at both short (up to 10 days)
and long (annual) temporal scales.
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
The total, organic and algal biomass of biofilms and their rates of net productivity in the
Mitta Mitta River are within the range of those found in other regulated south-east
Australian upland streams (see review in Burns & Ryder 2001b). Similarly, the low levels
of these attributes recorded from the unregulated reference river, Snowy Creek, were
similar to those from reference rivers in the headwaters of the Murrumbidgee catchment
used by Watts et al (2001). The stark differences between the biofilms in Snowy Creek and
the Mitta Mitta River highlight the impact of flow regulation on instream biofilm
communities.
Comparison of the effect of two variable flow releases and three variable flow releases on
biofilm attributes in permanently inundated cobble habitat.
The sloughing or scouring of biofilms is an important process in regulating sediment
accumulation and resetting biofilm structure (Peterson 1996; Mosisch & Bunn 1997) and
function (Bunn et al. 1999). The release of three successive flow peaks as part of the CRP
resulted in the significant reduction of biofilm dry weight and organic biomass at all sites
in the Mitta Mitta River when compared to biofilms developed under prolonged and
constant low flow conditions. Results from two successive variable flow releases were not
as conclusive. This suggests that the magnitude and shape of the three successive variable
releases were sufficient to ‘reset’ permanently inundated benthic algal communities
through mechanisms such as scouring along the entire study reach. Determining the effects
of individual and/or successive variable flow releases is difficult as data were not obtained
for the period prior to or during the first release.
The relative biovolume and species composition of permanently inundated biofilms
changed rapidly, while species richness remained static throughout the CRP. Significant
losses of biomass as a result of three successive variable flow releases may be due to shifts
in algal communities from ones dominated by filamentous green and blue-green taxa on
sample date 1 to biofilms dominated by diatoms at the end of the flow peak of variable
flow releases at both sites. This suggests the cumulative effect of three releases is to favour
early successional algal species, particularly evident by the dominance of early
successional diaton species such as Fragillaria sp. and Achnanthidium sp. at sites 1 and 4.
The rapid changes in the dominance of different algal divisions associated with changes in
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
discharge magnitude and variability during the releases may favour a diversity of primary
consumers in the Mitta Mitta River.
Similar to changes in taxonomic structure, the net productivity of permanently inundated
biofilms varied substantially during the CRP, as the balance between autotrophy and
heterotrophy within a biofilm is often determined by physical disturbances (Peterson
1996). The most obvious trend is the reduction in net productivity following the peak flows
of each release. This reduction in net productivity occurs concurrently with a 250 fold
increases in heterotrophic activity in the water column (section 3). We hypothesise that the
peak flows of 4800 ML/day are sufficient to result in the physical abrasion and damage of
algal cells along the entire study reach leading to an increase in heterotrophic microbial
productivity. This depression in net productivity is short lived, with rates of oxygen
production rising rapidly by the end of the second variable flow release. Scouring events
have been shown to favour the exponential growth phase of filamentous algal biofilms
attached to cobble (Uehlinger et al. 1996; Biggs & Stokseth 1996) which can promote high
levels of biofilm productivity through rapid increases in biomass (Ryder in press). This is
evident particularly at site 1, where a reduction in filamentous algal species by
approximately 50% immediately following the flow peak returns to a biofilm comprising
over 90% filamentous green and blue green algae. Similarly, peaks and troughs of biofilm
productivity in permanently inundated biofilms follow trends in the relative biovolume of
Stigeoclonium, filamentous green algae.
Comparisons of biofilm attributes in permanently inundated and newly inundated cobble
habitat.
An increase in the diversity of biofilm structure and function in the Mitta Mitta River by
creating habitats of newly inundated cobble was evident during the CRP. The wetting and
drying of biofilms has been shown to significantly alter their structure and function (e.g.
Fisher et al. 1982; Jowett and Duncan 1990, Άcs and Kiss 1993, Benenati et al. 1998,
Burns and Walker 2000, Ryder in press). Newly inundated cobble was generally lower in
total and organic biomass and consistently lower in Chl-a concentrations. The taxonomic
composition was similar between newly and permanently inundated biofilms, however the
relative dominance of different taxa was different between habitats. However, there were
no consistent trends in biofilm structural or composition attributes over time to suggest that
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
there were cumulative ecological benefits of three over two peak variable flow releases for
newly inundated biofilms.
However, the net productivity of newly inundated biofilms showed a trend of increasing
productivity between day 1 and 8 of each variable flow release, and between 2 and 3
variable flow releases. Biofilm net productivity was negative on the first day of inundation
associated with the flow peaks of variable flow release 2 and 3. Rewetting of biofilms
following desiccation has been shown to enhance rates of respiration in many systems as it
can respond more rapidly to rewetting than production (Sabater and Romani 1996, Romani
and Sabater 1997). However by day 8 of each variable flow release the net productivity
had increased substantially indicating the rapid response of biofilm metabolism to
rewetting. By day 8 of the third variable flow release, net productivity in the newly
inundated biofilms were strongly autotrophic and similar to rates in the permanently
inundated biofilms even though newly inundated biofilms had significantly lower Chl-a
concentrations. Differential responses by algal taxa to survive desiccation may be
responsible for increased productivity in these biofilms, with Chlorophytes and
Cyanobacteria showing the greatest resistance to desiccation (Davis 1972). This is
consistent with Ryder (in press) who found biofilm net productivity was enhanced by
wetting and drying cycles that promoted desiccation tolerant algal taxa. The recovery of
biofilms following desiccation can vary from days to months depending on the duration,
frequency and the speed of the drying process (Dodds et al. 1996, Benenati et al. 1998,
Biggs et al. 1999). It may therefore be possible to enhance the productivity of biofilms
through regulating the rates of rises and falls in water levels in the Mitta Mitta River.
However the slow drying of biofilms is necessary for surviving desiccation (Davis 1972)
and increasing their recovery potential (Robson 2000). Rapid rises and falls in water levels
(over days) in the Mitta Mitta River may be detrimental to biofilm productivity by
preventing the establishment of desiccation tolerant algal taxa (Ryder in press).
Effect of 37 days of constant flows on biofilm attributes in permanently inundated cobble
Under conditions of low to moderate disturbance, accrual processes dominate biofilm
development, especially where resources are not limited (Biggs 1996). This is evident at all
sites in the Mitta Mitta River where significant increases in total and organic biomass
occur at all sites during the period of lower and constant flows. These changes were not
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
evident in the reference river. This period also led to substantial changes in the taxonomic
composition and relative biovolume of major algal divisions at site 4. The filamentous
green algae Stigeoclonium, which requires substantial water velocities to support its
branching form was completely replaced by Oedogonium, a late successional taxon that
thrives in low velocity habitats (Burns & Walker 2000). More dramatic was the change to a
biofilm with 2 species of blue-green algae comprising over 95% of the biovolume by the
last sample date at site 4. These changes in biofilm composition may be directly related to
the flow velocity being insufficient to disturb the ‘boundary layer’ of algal cells. The
disturbance of the outer layers of algal cells within biofilms allows the transfer of organic
and inorganic nutrients and matter in and out of the biofilm (Peterson 1996). The two
species of blue-green algae, which dominate site 4 are capable of internally fixing their
own nitrogen, and are therefore not as reliant on external supplies of nutrients as other
taxa, and may have led to their complete dominance of the biofilm assemblage.
The period of lower and constant flows at the end of the CRP also led to a rapid decrease
in net productivity to a point where biofilms at site 4 were net consumers of oxygen. The
change in flow conditions from high flows that promoted large assemblages of filamentous
algae such as Stigeoclonium, Lyngbya and Planktothrix to low velocity and constant flows
over a relatively rapid period resulted in the death of large proportions of these algae.
These algae formed dense mats of rotting organic matter that coated the cobble and
remained attached to cobble due to persistent low velocity conditions. This material
provides a large resource to benthic heterotrophic bacteria which increases their activity
and biomass and reduces net biofilm productivity. Once biofilm communities have reached
this state, major changes to their structure and function may only be achieved by increases
in flow magnitude or variability.
6.5
•
Summary of Findings
The implementation of the CRP resulted in substantial changes to the structure and
function of biofilms through changes in water velocity and the creation of newly
inundated cobble areas through variable discharge volumes. However, many of these
changes associated with the CRP were short lived, with the period of constant flows
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
following the variable releases resulting in biofilms with a high biomass, a very low net
productivity and dominated by few species of algae.
•
Following the release of three successive variable flow releases there was a reduction
in biofilm dry and organic weight and a shift towards biofilm communities dominated
by early successional algal species at all sites in the Mitta Mitta River. This suggests
that the magnitude and shape of the three successive variable releases were sufficient to
scour algae and sediment from the permanently inundated cobble and reset biofilm
development along the entire study reach.
•
A substantial and rapid change in net productivity of biofilms was evident as a result of
the CRP, providing a diversity of productivity rates along the entire length of the study.
Flow peaks caused a reduction in net productivity from increased heterotrophic
microbial activity associated with scouring of algal cells. This depression in net
productivity is short lived, with rates of oxygen production rising rapidly by the end of
the second variable flow release.
•
A diversity in the structure and function of biofilms in The Mitta Mitta River was
evident as a result of the CRP by creating habitats of newly inundated cobble. Newly
inundated cobble was generally lower in total and organic biomass and Chl-a
concentrations, and altered the relative dominance of algal species compared to
permanently inundated cobble. The net productivity of newly inundated biofilms
showed a trend of increasing productivity between day 1 and 8 of each variable flow
release, and between 2 and 3 releases suggesting cumulative effects of successive flows
as part of the CRP.
•
All sites in the Mitta Mitta River displayed significant increases in total and organic
biomass occur during the period of lower and constant flows. These changes were not
evident in the reference river. This period also led to changes in the taxonomic
composition and relative biovolume of major algal divisions at site 4, and a rapid
decrease in net productivity to a point where biofilms at site 4 were net consumers of
oxygen. Once biofilm communities have reached this state, major changes to their
structure and function may only be achieved by increases in flow magnitude or
variability.
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
7.0 MACROINVERTEBRATES
7.1
Introduction
Freshwater macroinvertebrates are non-vertebrate animals (eg. insects, crustaceans, snails
and worms) that are visible to the naked eye and live at least part of their life within a body
of freshwater. Macroinvertebrates have been used in biological monitoring programs
worldwide as many taxa respond to changes in environmental conditions. In addition,
many species live for months or years, so they can integrate the impacts on the ecosystem
over an extended period of time, rather than just at the time of sampling.
Several macroinvertebrate indices have been developed to assess ecosystem health. Indices
such as the British River Invertebrate Prediction and Classification Scheme
(RIVPACS)(Wright
1995)
and
the
Australian
River
Assessment
System
(AusRivAS)(Simpson et al. 1997) compare the macroinvertebrate community structure at a
test site with that at reference sites. In these indices, poorer environmental conditions are
usually associated with a loss of taxa. Macroinvertebrate indices have also been developed
to monitor the ecological response to specific environmental stressors, such as pollution.
Examples of these types of biotic indices include the Biological Monitoring Working Party
Score (BMWP)(Chesters 1980, cited in Mason 1991) and the SIGNAL biotic index of
Chessman (1995). These indices are calculated from scores that have been assigned to
macroinvertebrate families, depending on their susceptibility to disturbance and pollution.
Higher levels of disturbance or pollution are generally associated with lower BMWP or
SIGNAL scores.
Macroinvertebrate indices have also been used to assess the impact of river regulation on
aquatic ecosystems. Many studies have shown there are differences in macroinvertebrate
species richness and community composition between regulated and unregulated river
reaches (eg. Brittain & Saltveit 1989; Richter et al. 1995). Other studies have observed a
reduction in the diversity of macroinvertebrates following construction of an impoundment
(eg. Armitage 1984; Doeg 1984; Boon 1988; Pardo et al. 1998).
Recently there has been a move towards reinstating elements of natural flow regimes in
regulated rivers as a means of river restoration. However, there is a considerable gap in
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
knowledge as to how biological indicators will respond to the changed flow conditions
(Watts & Ryder 2001). The highly predictable associations between macroinvertebrate
attributes and hydrological variables reported by Watts et al (2001) suggests that
macroinvertebrates can be used to provide a reliable assessment of the ecological impact of
changed flow management at relatively short temporal scales. Results from studies that
have compared macroinvertebrate indices between regulated and unregulated rivers (eg.
Brittain & Saltveit 1989; Richter et al. 1995) can be used to make predictions of the
changes expected following changed flow management.
The aim of the current project is to examine the response of macroinvertebrates to the CRP
in the Mitta Mitta River, Victoria. The ecological condition of the Mitta Mitta River is
expected to improve in response to the CRP. The following hypotheses will be examined
by this study:
1. There will be an increase in the diversity of macroinvertebrate families in the
Mitta Mitta River following the CRP relative to the diversity of
macroinvertebrate families in the reference reach Snowy Creek.
2. There will be an increase in the abundance of macroinvertebrate individuals in
the Mitta Mitta River following the CRP relative to the abundance of
macroinvertebrate individuals in the reference reach Snowy Creek.
3. There will be an increase in the SIGNAL scores in the Mitta Mitta River following
the CRP relative to any changes in the SIGNAL score in the reference reach
Snowy Creek
7.2
Methods
7.2.1 Field methods-Cobble habitats
Macroinvertebrates in cobble habitats were sampled quantitatively using a surber sampler
comprising a rectangular quadrat (20cm by 20cm) to delineate the area of bed to be
sampled and a net (250 µm mesh) into which the disturbed benthic invertebrates are swept
by the current. The sampler was placed on the benthos facing upstream and the substrate
within the quadrat was thoroughly disturbed. Following sampling, net contents were
emptied into a labelled sample jar and were preserved in 70% alcohol. Macroinvertebrates
from permanently inundated cobble banks were sampled on nine sampling dates (Table
2.2) from four sites in the Mitta Mitta River and one site on Snowy Creek (Figure 2.1).
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
Macroinvertebrates from newly inundated cobble banks on cobble banks were sampled on
four sampling dates (2, 3, 5 and 6 in Table 2.2) from only the four sites in the Mitta Mitta
River (Figure 2.1). Four replicates were collected from each site on each sampling date.
7.2.2 Field methods-Littoral habitats
Macroinvertebrates in littoral areas at each site were sampled qualitatively using a sweep
net. Sampling involved vigorously sweeping the net through the water column around
overhanging vegetation and snags. Following sampling, net contents were emptied into a
labelled sample jar and were preserved in 70% alcohol.
7.2.3 Laboratory methods
All invertebrates were removed from each sample using a dissecting microscope and were
stored in 70% ethanol. Fauna from the surber samples were counted and identified to
family level. Fauna from qualitative sweep samples were identified to family level.
7.2.4 Data Manipulation and Analyses
The raw data were used to calculate the following attributes for each habitat (permanently
inundated cobble, newly inundated cobble) at each site on each sampling date:
• Mean and standard error of number of Families;
• Mean and standard error of number of individuals;
• SIGNAL scores based on Chessman (1995)
The mean number of families and mean number of individuals were compared between
dates within each site using single-factor ANOVA. The following planned comparisons
were undertaken:
1. Date 1 (end of first variable flow release) to date 4 (end of second variable flow
release) and date 1 to date 7 (end of third variable flow release) for each of the five
sites to examine the individual and cumulative effects of the second and third variable
flow releases.
2. Permanently inundated cobble to newly inundated cobble habitat for sites 1 to 4 in the
Mitta River for each of the sample date 2 (flow peak of second variable flow release),
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
date 3 (day 8 of second variable flow release), date 5 (flow peak second of flow
release) and date 6 (day 8 of third variable flow release).
3. Date 7 (end of flow release 3 and start of constant flows) to date 9 (end of constant
flow period) to examine the effect of 37 days of constant flows.
Macroinvertebrate
community
composition
was
analysed
using
non-metric
multidimensional scaling (NMDS), analysis of similarities (ANOSIM) and species
contributions to similarities (SIMPER) analyses available in the software package
PRIMER (Clarke and Warwick 1994). The Bray-Curtis distance measure was used to
generate the similarity matrix using square root transformed data. NMDS is a method of
summarising multivariate species data where the similarity between sites is represented
graphically in an ordination. The more similar the sites are in species composition, the
closer they will group together within the ordination. The ANOSIM routine in Primer
(Clarke and Warwick 1994) was used to carry the same three a priori comparisons as used
in the ANOVA. ANOSIM analysis computes an R statistic that reflects the differences
between treatments. Clarke and Gorley (2001) advise the following levels of R
interpretation:
R=1
complete separation of treatments
R > 0.75
treatments are well separated
R > 0.5
treatments may be overlapping but are still clearly different
R < 0.25
treatments are barely separable
The SIMPER routine was used to identify the families that contributed to the significant
differences between groups identified by the ANOSIM analysis.
7.3
Results
7.3.1 Overview of macroinvertebrate data
There were a total of 53 families of macroinvertebrates collected in the cobble habitat
during this study. Twelve families were in the order Coleoptera, ten families in the order
Trichoptera (caddis flies), eight families in the order Diptera (two winged flies), four
families in the order Ephemeroptera (mayflies) and three families in the order Plecoptera
(caddis flies).
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
In general, site one had fewer macroinvertebrate families than all of the other sites (Figure
7.1). The mean number of families in the permanently cobble habitat at site one increased
by 175% between dates one and nine, whereas other sites showed relatively smaller
increases (eg site 2) or very little change at all (eg. site 3). The mean number of families in
the newly inundated cobble was generally lower than that in the permanently inundated
cobble at the beginning of the second variable flow release, but was similar to that in the
permanently inundated cobble by date 6 (Figure 7.1)
The numbers of macroinvertebrate families in littoral habitats varied considerably between
sample dates at all sites, including the reference site (Figure 7.2). This suggests that factors
other than flow may influence this parameter and that the qualitative sweep method used to
sample the littoral habitats may not be as reliable for the assessment of CRP as the
quantitative surber sample method used in the cobble habitat.
There was considerable variation in the number of macroinvertebrate individuals in the
cobble habitat on different sampling dates. During the 37 days of constant flows following
the CRP there was an increase in the number of individuals at sites two and three (Figure
7.3).
The SIGNAL scores for the macroinvertebrate assemblage in the cobble habitat were
lowest at site one (Figure 7.4). The SIGNAL score at site one increased from 4.00 on
sample date one to 6.18 on date nine. There was not a similar increase in SIGNAL scores
at the other sites. The three sites in the Mitta Mitta River had scores that fluctuated around
6.0 (range 5.3 to 6.6) and Snowy Creek generally had a slightly higher SIGNAL score
ranged from 6.3 and 7.15.
In general, the macroinvertebrate community assemblage in the newly inundated cobble
habitat was different to that in the permanently inundated cobble on sampling dates 2 and 3
(Figure 7.5). The macroinvertebrate assemblage in newly inundated cobble tended to
become more similar to that in the permanently inundated cobble by date 6 (day 8 of the
second variable flow release) (Figure 7.5). The two-dimensional ordinations (Figure 7.5)
all had low stress values (range 0.06 to 0.14) which suggests that these ordinations reliably
summarise the relationships between sample dates.
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
14
Site 1
12
10
8
6
4
Newly inundated
Permanently inundated
2
0
14
2/12/01
9/12/01
16/12/01
23/12/01
30/12/01
6/01/02
13/01/02
20/01/02
27/01/02
3/02/02
13/01/02
20/01/02
27/01/02
3/02/02
13/01/02
20/01/02
27/01/02
3/02/02
13/01/02
20/01/02
27/01/02
3/02/02
Site 2
12
10
8
6
4
2
0
2/12/01
9/12/01
16/12/01
23/12/01
30/12/01
14
6/01/02
Site 3
12
10
8
6
4
2
0
2/12/01
9/12/01
16/12/01
23/12/01
30/12/01
14
6/01/02
Site 4
12
10
8
6
4
2
0
2/12/01
9/12/01
16/12/01
23/12/01
30/12/01
14
6/01/02
Site 5
12
10
8
6
4
2
0
2/12/01
16/12/01
30/12/01
13/01/02
27/01/02
Figure 7.1: Number of macroinvertebrate families in permanently inundated and newly inundated
cobble habitat at four sites in the Mitta Mitta River (sites 1-4) and one site in Snowy Creek (site 5).
(mean ± SE, n = 4).
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
Number Families
30
Site 1
25
20
15
10
5
0
2/12/01
9/12/01
16/12/01
23/12/01
30/12/01
6/01/02
13/01/02
20/01/02
27/01/02
3/02/02
13/01/02
20/01/02
27/01/02
3/02/02
30
Site 2
Number Families
25
20
15
10
5
0
2/12/01
9/12/01
16/12/01
23/12/01
30/12/01
6/01/02
30
Site 3
Number Families
25
20
15
10
5
0
2/12/01
9/12/01
16/12/01
23/12/01
30/12/01
6/01/02
13/01/02
20/01/02
27/01/02
3/02/02
13/01/02
20/01/02
27/01/02
3/02/02
30
Site 4
Number Families
25
20
15
10
5
0
2/12/01
9/12/01
16/12/01
23/12/01
30/12/01
6/01/02
30
Number Families
Site 5
25
20
15
10
5
0
2/12/01
16/12/01
30/12/01
13/01/02
27/01/02
Figure 7.2: Number of macroinvertebrate families in littoral habitat at four sites in the Mitta Mitta
River (sites 1-4) and one site in Snowy Creek (site 5).
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
300
Newly inundated
Site 1
Permanently inundated
250
200
150
100
50
0
2/12/01
300
9/12/01
16/12/01
23/12/01
30/12/01
6/01/02
13/01/02
20/01/02
27/01/02
3/02/02
Site 2
250
200
150
100
50
0
2/12/01
9/12/01
16/12/01
23/12/01
30/12/01
300
6/01/02
13/01/02
20/01/02
27/01/02
3/02/02
Site 3
250
200
150
100
50
0
2/12/01
9/12/01
16/12/01
23/12/01
30/12/01
300
6/01/02
13/01/02
20/01/02
27/01/02
3/02/02
13/01/02
20/01/02
27/01/02
3/02/02
Site 4
250
200
150
100
50
0
2/12/01
9/12/01
16/12/01
23/12/01
30/12/01
6/01/02
300
Site 5
250
200
150
100
50
0
2/12/01
16/12/01
30/12/01
13/01/02
27/01/02
Figure 7.3: Number of macroinvertebrate individuals in permanently inundated and newly
inundated cobble habitat at four sites in the Mitta Mitta River (sites 1-4) and one site in Snowy
Creek (site 5). (mean ± SE, n = 4)
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
91
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
8
7
6
5
4
3
2
1
0
2/12/01
8
Site 1
Newly inundated
Permanently inundated
9/12/01
16/12/01
23/12/01
30/12/01
6/01/02
13/01/02
20/01/02
27/01/02
3/02/02
13/01/02
20/01/02
27/01/02
3/02/02
13/01/02
20/01/02
27/01/02
3/02/02
13/01/02
20/01/02
27/01/02
3/02/02
Site 2
7
6
5
4
3
2
1
0
2/12/01
9/12/01
16/12/01
23/12/01
30/12/01
6/01/02
8
Site 3
7
6
5
4
3
2
1
0
2/12/01
9/12/01
16/12/01
23/12/01
30/12/01
6/01/02
8
Site 4
7
6
5
4
3
2
1
0
2/12/01
9/12/01
16/12/01
23/12/01
30/12/01
6/01/02
8
Site 5
7
6
5
4
3
2
1
0
2/12/01
16/12/01
30/12/01
13/01/02
27/01/02
Figure 7.4: SIGNAL scores in permanently inundated and newly inundated cobble habitat at four
sites in the Mitta Mitta River (sites 1-4) and one site in Snowy Creek (site 5).
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
Site 1
5N
1P
6N 5P
3P
6P
9P
2P
4P
3N
2N
7P
8P
Stress: 0.06
Site 2
9P
6N
6P
2N
8P
5N
3N
3P
1P
7P 4P5P
2P
Stress: 0.07
8P
Site 3
7P
5N
5P
3P
2P
6P
4P
6N
1P
2N
3N
9P
Stress: 0.1
6N
1P
3P
Site 4
6P
3N
4P
5P
2P
1P
3P
6N
5N
6P
5P
4P
3N
9P
7P
8P
2N
9P
7P
5N
Stress: 0.01
8P
Stress: 0.14
Site 5
5P
6P
3P
7P
8P
4P
1P
2P
9P
Stress: 0.11
Figure 7.5: NMDS ordination of macroinvertebrate assemblage from permanently inundated (P)
and newly inundated (N) cobble in the Mitta Mitta River (sites 1-4) and Snowy Creek (site 5) over
nine sampling dates. For details of sampling dates see Table 1.2.
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
Comparison of the effect of two variable flows and three variable flows on
macroinvertebrates in permanently inundated cobble habitat.
There was no significant increase in the number of macroinvertebrate families in the
permanently inundated cobble at any of the sites between the beginning and the end of the
second variable flow release (date 1 and 4)(Table 7.1, Figure 7.1). However, by the end of
the third variable flow release (date 7) there was a significant increase in the number of
families at site one. This occurred over a period of time when there was no change in the
number of families at the reference site (site 5 Snowy Creek)(Table 7.1, Figure 7.1). There
was no significant change in the number of individuals at all permanently inundated cobble
sites between the beginning and the end of the second variable flow release (date 1 and
4)(Table 7.2, Figure 7.3). There was a significant decrease in the number of individuals at
site 3 by the end of the third variable flow release (date 7).
The results of the ANOSIM analyses (Table 7.3) show that there were no significant
changes in the composition of the macroinvertebrate community in the reference site
Snowy Creek during the period when the CRP was conducted in the Mitta Mitta River.
However, there were differences in community composition in the permanently inundated
cobble habitat at site four by the end of the second variable flow release (date 4) and at site
one, three and four by the end of the third variable flow release (date 7)(Table 7.3). The
NMDS ordinations (Figure 7.5) demonstrate graphically the changes occurring in the
macroinvertebrate community over time. These ordinations show that at site one, three and
four the macroinvertebrate community in the permanently inundated cobble at the
beginning of the second variable flow (date 1P) is quite different to that at the end of the
CRP (date 7P).
Table 7.4 lists the families that made the greatest contribution to the difference in
community composition between sampling dates. At sites one, three and four in the Mitta
Mitta River between sample date one and seven there was a decrease in the abundance of
Chironomidae and increase in the abundance of Oligochaeta (Table 7.4). At site one there
was an increase in the abundance of the families Caenidae, Coloburiscidae and
Griptopterygidae by date 7, resulting in a 45% increase in SIGNAL score over this period
(SIGNAL score increased from 4.00 to 5.83)(Table 7.5). Whereas, at site three and four
there were decreases in the families Caenidae, Leptophlebidae and Gripopterygidae, but
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
94
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
increases in other families such as Coloburiscidae at site 3 and Glossosomatidae at site 4
(Table 7.4). Consequently, there was little change in the SIGNAL score at sites two, three
and four between dates one and seven (Table 7.5). Over the same period that there was an
increase in SIGNAL score at site one there was a decrease in SIGNAL score in the
reference site Snowy Creek (Table 7.5).
Table 7.1: Probability value and significance levels of one-way ANOVA’s comparing number of
macroinvertebrate families in permanently inundated cobble habitats between sample dates 1 and
4 and between dates 1 and 7 at four sites in the Mitta Mitta River (sites 1 to 4) and in Snowy Creek
(site 5). Direction of trend is shown in brackets. ns = not significant, * = P < 0.05, ** = P < 0.01, ***
= P < 0.001.
Site
1. Mitta Mitta
2. Mitta Mitta
3. Mitta Mitta
4. Mitta Mitta
5. Snowy Creek
Two variable flows
(date 1 to date 4)
0.315 ns
0.031 * (1>4)
0.293 ns
0.560 ns
0.176 ns
Three variable flows
(date 1 to date 7)
0.000 *** (1<7)
0.620 ns
0.293 ns
0.138 ns
0.437 ns
Table 7.2: Probability value and significance levels of one-way ANOVA’s comparing number of
macroinvertebrate individuals in permanently inundated cobble habitats between sample dates 1
and 4 and between dates 1 and 7 at four sites in the Mitta Mitta River and in Snowy Creek.
Direction of trend in shown in brackets. ns = not significant, * = P < 0.05, ** = P < 0.01, *** = P <
0.001.
Site
1. Mitta Mitta
2. Mitta Mitta
3. Mitta Mitta
4. Mitta Mitta
5. Snowy Creek
Two variable flows
(date 1 to date 4)
0.857 ns
0.411 ns
0.126 ns
0.082 ns
0.318 ns
Three variable flows
(date 1 to date 7)
0.285 ns
0.144 ns
0.009 ** (1>7)
0.390 ns
0.535 ns
Table 7.3: R values and significance levels of ANOSIM analyses comparing macroinvertebrate
faunal assemblages on permanently inundated cobble between sampling dates at five sites in the
Mitta Mitta River. ns = not significant and *= P<0.05.
Site
1. Mitta Mitta
2. Mitta Mitta
3. Mitta Mitta
4. Mitta Mitta
5. Snowy Creek
Two variable flows
(date 1 to date 4)
-0.063 ns
-0.052 ns
0.354 ns
0.869 *
0.313 ns
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
Three variable flows
(date 1 to date 7)
0.594 *
0.063 ns
0.719 *
0.979 *
0.583 ns
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
Table 7.4: Abundance of macroinvertebrate families that contributed significantly to the SIMPER
analyses comparing permanently inundated cobble habitat between dates 1 and 4, and 1 and 7.
The % contribution to the SIMPER analyses is shown for each comparison. Comparisons shown to
be significant by the ANOSIM analyses are highlighted.
Site 1
Site 2
Site 3
Site 4
Site 5
Average abundance of
macroinvertebrate Families on
each sample date
Date 1
Date 4
Date 7
25.0
8.2
7.0
3.8
9.2
34.0
1.8
2.0
2.5
0
0
2.5
0
1.5
5.2
8.0
8.0
2.0
1.2
1.2
2.2
6.0
2.0
2.0
3.0
2.5
2.2
48.2
14.5
1.0
0.5
2.0
1.2
7.2
3.8
0.2
0.2
1.5
2.8
2.5
3.0
1.2
5.5
6.5
4.0
21.0
33.8
6.0
1.8
6.8
13.0
1.8
0.5
0.2
2.2
0
0.8
0
2.0
11.0
6.0
0.5
2.2
1.5
3.0
0.8
17.0
17.5
16.0
0
1.0
1.2
6.5
8.8
10.8
1.2
1.5
0
2.0
2.2
11.0
1.8
2.2
0.2
Family
Chironomidae
Oligochaeta
Caenidae
Coloburiscidae
Griptopterygidae
Chironomidae
Oligochaeta
Caenidae
Leptophlebiidae
Chironomidae
Oligochaeta
Caenidae
Coloburiscidae
Griptopterygidae
Leptophlebiidae
Chironomidae
Oligochaeta
Caenidae
Coloburiscidae
Glossosomatidae
Leptophlebiidae
Griptopterygidae
Chironomidae
Coloburiscidae
Leptophlebiidae
Glossosomatidae
Baetidae
Gripopterygidae
% contribution to SIMPER
Date 1 vs 4
37.3
20.1
15.9
0
11.8
40.6
8.1
21.9
13.0
58.6
3.0
6.8
2.6
3.7
7.8
37.5
15.0
3.3
6.4
5.7
15.9
4.6
16.5
4.2
5.7
5.6
4.8
4.4
Date 1 vs 7
17.8
24.2
8.7
9.5
17.9
33.6
11.6
22.8
8.9
64.0
2.1
9.1
3.4
2.2
6.8
26.9
19.8
2.8
4.0
19.0
7.8
2.1
15.7
7.2
6.6
4.9
11.6
6.7
Table 7.5: SIGNAL scores for macroinvertebrate samples from four sites in the Mitta Mitta River
and in Snowy Creek for sample dates 1, 4 and 7.
Site
1. Mitta Mitta
2. Mitta Mitta
3. Mitta Mitta
4. Mitta Mitta
5. Snowy Creek
Date 1
4.00
6.60
6.20
6.00
7.00
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
Date 4
4.71
6.00
6.31
6.08
6.63
Date 7
5.83
6.56
6.00
6.14
6.35
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
Comparison of macroinvertebrates in permanently inundated and newly inundated cobble
habitat
On the peak of the second variable flow release (date 2) there were significantly fewer
macroinvertebrate families in the newly inundated cobble habitat than in the permanently
inundated cobble habitat at three of the four sites in the Mitta Mitta River (Table 7.6,
Figure 7.1). However, by the eighth day of the third variable flow release (date 6) there
were a similar number of families in the newly inundated and permanently inundated
habitat at three of the four sites (Table 7.6, Figure 7.1).
On the peak of the second variable flow release (date 2) there were significantly fewer
individuals in the newly wetted cobble habitat than in the permanently inundated cobble
habitat at all of the four sites in the Mitta Mitta River. However, by the eighth day of the
third variable flow release (date 6) at all sites there was no difference in the number of
individuals in the newly inundated and permanently inundated cobble habitat (Table 7.7,
Figure 7.3).
The community composition of macroinvertebrates in the newly inundated cobble habitat
was, in general, different to that in the permanently inundated cobble habitat at all of the
four sites in the Mitta Mitta River on dates 2, 3 and 5 (Table 7.8, Figure 7.5). By the eighth
day of the third variable flow release (date 6) at all sites there was no significant difference
in the community composition between habitats (Table 7.8, Figure 7.5). With only one
exception (site 4, date 3), SIGNAL scores were the same or higher in the permanently
inundated cobble than in the newly inundated cobble on these dates (Table 7.9, Figure 7.4).
Several macroinvertebrate familes increased their abundance in the newly inundated
cobble habitat during the CRP. At site one there were several families (eg. Caenidae and
Coloburiscidae) absent from the newly inundated cobble on dates two, four and five that
had colonised this habitat by date 6. Table 7.10 lists the families that made the greatest
contribution to the difference in community composition between newly inundated and
permanently inundated cobble habitat.
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
Table 7.6: Probability value and significance levels of one-way ANOVA for differences in number of
macroinvertebrate families between permanently inundated (P) and newly inundated (N) cobble
habitats at four sites in the Mitta Mitta River on four sample dates. Direction of trend in shown in
brackets. ns = not significant, * = P < 0.05, ** = P < 0.01, *** = P < 0.001.
Site
1
2
3
4
Date 2
0.168 ns
0.020 * (N<P)
0.001 *** (N<P)
0.010 ** (N<P)
Date 3
0.031 * (N<P)
0.219 ns
0.027 * (N<P)
0.339 ns
Date 5
0.445 ns
1.000 ns
0.039 * (N<P)
0.003 ** (N<P)
Date 6
0.260 ns
1.000 ns
0.025 * (N<P)
0.689 ns
Table 7.7: Probability value and significance levels of one-way ANOVA for differences in total
number of macroinvertebrate individuals between permanently inundated (P) and newly inundated
(N) cobble habitats at four sites in the Mitta Mitta River on four sample dates. Direction of trend in
shown in brackets. ns = not significant, * = P < 0.05, ** = P < 0.01, *** = P < 0.001.
Site
1
2
3
4
Date 2
0.010 **
0.001 **
0.043 *
0.000 ***
(N<P)
(N<P)
(N<P)
(N<P)
Date 3
0.006 ** (N<P)
0.185 ns
0.503 ns
0.819 ns
Date 5
0.172 ns
0.288 ns
0.031 * (N<P)
0.001 ** (N<P)
Date 6
0.236 ns
0.731 ns
0.244 ns
0.218 ns
Table 7.8: R values and significance level of ANOSIM analyses comparing macroinvertebrate
faunal assemblages between permanently inundated and newly inundated cobble at four sites in
the Mitta Mitta River. All comparisons were based on 25 permutations, with the exception of site 3,
date 2 which had 15 permutations. ns = not significant and *= P<0.05.
Site
1
2
3
4
Date 2
0.396 *
0.857 *
0.969 *
No test
Date 3
0.313 *
0.047 ns
0.885 *
0.813 *
Date 5
0.500 *
0.365 *
0.573 *
0.906 *
Date 6
0.240 ns
0.063 ns
0.219 ns
0.260 ns
Table 7.9: Comparison of SIGNAL scores for macroinvertebrates collected from permanently
inundated and newly inundated cobble habitat in the Mitta Mitta River on four sample dates. P =
permanently inundated cobble, N = newly inundated cobble.
Site
1
2
3
4
Date 2
P
4.83
7.00
6.25
6.50
N
4.25
7.00
4.33
No data
Date 3
P
4.71
6.40
6.53
5.38
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
N
3.00
5.78
5.82
5.50
Date 5
P
5.00
5.86
6.18
5.88
N
3.33
4.78
4.38
4.33
Date 6
P
5.83
5.73
6.19
6.15
N
5.07
5.73
5.92
5.43
98
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
Table 7.10: Average abundance of macroinvertebrate families that contributed significantly to the
SIMPER analyses comparing permanently inundated and newly inundated cobble habitat on four
sample dates. P = permanently inundated cobble, N = newly inundated cobble, % = percent
contribution to difference. Av Dissim = Average Dissimilarity. Comparisons shown to be significant
by the ANOSIM analyses are highlighted.
Site 1
Family
Chironomidae
Oligochaeta
Caenidae
Coloburiscidae
Griptopterygidae
Site 2
Family
Chironomidae
Oligochaeta
Caenidae
Coloburiscidae
Griptopterygidae
Leptophlebiidae
Site 3
Family
Chironomidae
Oligochaeta
Caenidae
Coloburiscidae
Griptopterygidae
Leptophlebiidae
Hydropsychidae
Conoescucidae
Glossosomatidae
Site 4
Family
Chironomidae
Oligochaeta
Caenidae
Coloburiscidae
Griptopterygidae
Leptophlebiidae
Hydropsychidae
Conoescucidae
Glossosomatidae
Baetidae
Date 2
(Av Dissim 79.3)
P
N
%
5.5
1.2 28.6
0.8
0 10.9
2.2
0 25.6
0
0
0
0.2
0
3.4
Date 3
(Av Dissim 84.5)
P
N
%
21.5
0.8 36.0
4.0
0.5 12.9
5.8
0 21.8
0.5
0
7.0
1.5
0
8.8
Date 5
(Av Dissim 72.1)
P
N
%
21.0
3.8 22.5
34.2
3.2 26.4
2.8
0 11.5
1.0
0 10.0
0
0.2
2.0
Date 6
(Av Dissim 57.4)
P
N
%
20.8 14.2 15.5
10.5 63.8 33.5
9.0
1.5 10.9
0.5
0.2
2.4
0.8
5.8 10.5
Date 2
(Av Dissim 100)
P
N
%
1.8
0 14.4
10.7
5.8
6.5
57.6
Date 3
(Av Dissim 60.0)
P
N
%
7.0 16.8 17.9
3.8 11.5 16.9
1.2
6.0 12.9
2
0 10.0
0.5
0.2
4.1
2.2
2
7.2
Date 5
(Av Dissim 64.1)
P
N
%
6.5
2.2 16.7
1.8
3 14.1
1.2
0.5
9.3
0.2
0
0
2.2 17.0
4.5
1 18.0
Date 6
(Av Dissim 38.4)
P
N
%
64.8 55.5 22.8
31.8
67 24.6
2.2
10 11.0
3
1.2
6.8
0.8
1.0
5.5
5.8
1.8
7.9
Date 2
(Av Dissim 69.6)
P
N
%
12.2 14.5 11.6
1
1.2
4.0
2.2
0.2
6.4
7.8
0 13.7
3.2
0.2
8.5
5.8
0.2 12.4
3.8
0 11.3
2.0
0
6.1
1.0
0
4.2
Date 3
(Av Dissim 71.0)
P
N
%
10.0 20.8 12.9
1.0 12.0
9.9
0.5
0.5
2.4
11.0
0 16.0
3.8
0.5
7.8
5.0
2.2
6.8
2.5
0.2
6.3
3.8
0
9.0
1.5
0
4.7
Date 5
(Av Dissim 61.4)
P
N
%
5.0
6.0
5.4
3.2
4.5
9.4
0.8
0
5.1
3.5
0 12.2
1.5
0.2
7.3
3.0
0 11.0
4.5
0 14.4
1.0
0
7.0
0.8
0
4.4
Date 6
(Av Dissim 51.3)
P
N
%
19.2 12.2 15.3
7.5
6.2
8.9
0.8
1.8
4.5
8.8
0 15.4
4.5
2.2
7.0
4.0
6.7
3.4
1.0
0
3.9
1.2
0
5.1
2.5
0
7.4
Date 2
(Av Dissim 69.6)
P
N
%
0.8
0 32.3
Date 3
(Av Dissim 71.0)
P
N
%
22.0 16.8 10.5
1.2
5.8 10.2
0
1.8
5.5
2.2
0
4.8
1
4.5
8.0
4.2
0.5
9.6
1.5
0
6.4
0.5
0
3.0
1.2
0
3.2
1.2
0
6.8
Date 5
(Av Dissim 61.4)
P
N
%
49.5
6.8 21.8
33.2
5.2 18.9
1.5
0
6.3
0
0.2
1.4
2.8
1.5
5.6
3.2
0
9.9
0.8
0
4.0
0.5
0
1.5
1.2
0
4.6
1.2
0
5.0
Date 6
(Av Dissim 51.3)
P
N
%
20.5 14.8 10.9
8.0 39.2 10.9
0.5
0.5
3.8
0.8
0.5
4.0
4.8
6.2
8.7
2.0
3.2
7.2
0.2
0
1.2
0.8
0
4.9
1.0
0
4.9
2.5
4.8
7.5
1
0.2
0
6.8
0
0
0.5
0
0.8
0.5
0
0
22.9
19.8
0.2
0
25.0
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
99
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
Effect of 37 days of constant flows on macroinvertebrates in permanently inundated cobble
At sites two and three there were significant increases in number of families in the
permanently inundated cobble over the 37 days of constant low flows following the CRP
(Table 7.11). At site two the increase resulted in a larger number of families recorded than
at any other time in the study (Figure 7.1). At site three the increase during the 37 days
constant flows returned the number of families to a previously observed level (Figure 7.1).
At sites two and three there were significant increases in number of individuals in the
permanently inundated cobble over the 37 days of constant low flows following the CRP
(Table 7.11, Figure 7.3). The increase in number of individuals was particularly marked at
site three.
There were significant changes in the community composition between sample dates seven
and nine at all five sites, including the reference site (Table 7.13). Accompanying these
changes the SIGNAL score at site one continued to increase. However, the SIGNAL score
at sites two and five decreased from date 7 to date 9 (Table 7.14).
The changes in community composition at sites one to four do not parallel that in the
reference site (Table 7.15). All four sites in the Mitta Mitta River showed increases in the
abundance of Chironomids and decreases in the abundance of Coloburiscidae between
dates seven and nine, whereas there was a decrease in the abundance of Chironomids and
increase in the abundance of Coloburiscidae in Snowy Creek between these dates (Table
7.15). All sites, including Snowy Creek, showed increases in Hydropsychidae during this
period (Table 7.15). The SIMPER data shows that the significant increases in the numbers
of individuals at sites two and three between dates 7 and 9 are due to increases in
Chironomidae and Oligochaeta.
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
100
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
Table 7.11: Probability value and significance levels of one-way ANOVA’s comparing number of
macroinvertebrate families between the end of the CRP (date 7) to the end of the 37 days constant
flows (date 9) in permanently inundated cobble habitats at four sites in the Mitta Mitta River and in
Snowy Creek. ns = not significant, * = P < 0.05. Direction of trend is shown.
Site
1
2
3
4
5 (ref)
Probability value
0.346
0.020
0.016
0.876
0.147
Significance level
ns
*
*
ns
ns
Post hoc test
7<9
7<9
Table 7.12: Probability value and significance levels of one-way ANOVA’s comparing number of
macroinvertebrate individuals between the end of the CRP (date 7) to the end of the 37 days
constant flows (date 9) in permanently inundated cobble habitats at four sites in the Mitta Mitta
River and in Snowy Creek. ns = not significant, * = P < 0.05, ** = P < 0.01, *** = P < 0.001.
Site
1
2
3
4
5 (ref)
Probability value
0.916
0.021
0.0002
0.511
0.718
Significance level
ns
*
***
ns
ns
Post hoc test
7<9
7<9
Table 7.13: Results of ANOSIM analyses comparing macroinvertebrate faunal assemblages on
permanently inundated cobble between the end of the CRP (date 7) and the end of 45 days
constant flows (date 10) at four sites in the Mitta Mitta River and in Snowy Creek. All comparisons
were based on 35 permutations. * = P<0.05.
Site
1
2
3
4
5 (ref)
R value
0.594
0.740
0.896
0.802
0.698
Probability value
0.029
0.029
0.029
0.029
0.029
Significance level
*
*
*
*
*
Table 7.14: SIGNAL scores for macroinvertebrate samples from four sites in the Mitta Mitta River
and in Snowy Creek for sample dates 7 and 9.
Site
1.
2.
3.
4.
5. (ref)
Date 7
5.83
6.56
6.00
6.14
6.35
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
Date 9
6.18
6.21
6.00
6.12
6.07
101
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
Table 7.15: Abundance of macroinvertebrate families that contributed significantly to the SIMPER analyses comparing permanently inundated cobble habitat
between dates 7 and 9. The % contribution to the SIMPER analyses is shown for each comparison. Comparisons shown to be significant by the ANOSIM
analyses are highlighted.
Family
Chironomidae
Oligochaeta
Caenidae
Coloburiscidae
Griptopterygidae
Leptophlebiidae
Hydropsychidae
Glossosomatidae
Baetidae
Tabanidae
Site 1
(Av Dissim 52.6)
Dat Dat %
e7
e9
7.0 20.2 12.0
34.0 12.8 13.5
2.5
2.5
7.3
2.5
0
7.6
5.2
1.0
9.9
0
2.5
9.7
0
0.8
2.5
0.5
0
4.4
0.2
0.5
3.1
0.2
1.8
4.9
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
Site 2
(Av Dissim 66.2 )
Dat Dat %
e7
e9
2.0 31.5 18.2
2.2 19.8 11.3
2.0
5.2
3.9
0.8
0.5
3.5
0.2
6.8 12.2
2.2
0.2
7.0
0
3.0
7.1
0
2.5
6.2
0
1.2
6.6
0
1.2
2.9
Site 3
(Av Dissim 76.2)
Dat Dat %
e7
e9
1.0 160 31.2
1.2 34.0 12.9
0.2
8.2
7.0
2.8
1.0
3.0
1.2
1.2
1.7
4.0
4.5
1.7
0.8 35.0 14.1
2.0
0.8
2.4
0.5
1.2
2.2
0
8.5
7.9
Site 4
(Av Dissim 54.4)
Dat Dat %
e7
e9
6.0 29.5 13.8
13.0 10.8
7.5
0.2
1.2
4.1
0.8
0.8
0.2
3.1
2.2
3.5
5.5
1.8
7.8
6.9
11.0
0 16.5
1.2
0
5.0
0
1.5
4.7
102
Site 5 (ref)
(Av Dissim 52.7)
Dat Dat %
e7
e9
16.0 11.5
9.4
0.2
0
1.2
0
0
0
1.2
6.8
8.1
0.2
1.5
4.7
10.8
9.2
4.5
0.5
2.5
5.1
0
4.5
8.7
11.0
1.5
9.4
0.2
0.8
3.0
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
7.4
Discussion
This study examined the effects of CRP from Dartmouth Dam to the Mitta Mitta
River on the species richness, abundance and community composition of
macroinvertebrates. The implementation of this release pattern resulted in significant
changes in the macroinvertebrate community, with the greatest effects being observed
at the most upstream site (site 1). Although the full extent of the response to CRP
could not be determined by this study (due to the lack of sampling prior to the CRP),
this study has demonstrated that it is possible to detect a response of
macroinvertebrates to the CRP.
Site one in the upper reaches of the Mitta Mitta River had fewer families and
considerably lower SIGNAL scores than the other sites in the Mitta Mitta River and
the reference site in Snowy Creek. This is consistent with the findings of a previous
study by AWT (2000), which found that SIGNAL scores in the Mitta Mitta River
were between 5.0 and 6.0, whereas the major tributary Snowy Creek, had a SIGNAl
score of 6.7. As site one is at a similar altitude and has similar adjacent land use to
Snowy Creek, this suggests that the poorer ecological condition at this site can be
largely attributed to the management of Dartmouth dam.
Macroinvertebrates were found to respond relatively rapidly to the individual variable
flow releases. After only 14 days there was a significant change in the community
assemblage at site 4. After 28 days there was a significant increase in the number of
macroinvertebrate families at site one in the Mitta Mitta River and significant changes
in the community assemblage at sites 1, 3 and 4. These relatively rapid responses are
consistent with the results of Watts et al (2001), who found that there were highly
predictable associations between macroinvertebrate attributes and hydrological
variables at both short (10 and 30 days) and long (year) temporal scales.
The greatest effect of the CRP was observed at site one, the most upstream site. At
this site there was a significant increase in macroinvertebrate families, a significant
change in community composition and a substantial increase in SIGNAL scores in
permanently inundated cobble by the end of the third variable flow release. Changes
in the composition of the macroinvertebrate assemblage were also observed at sites
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
103
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
three and four by the end of the third variable flow, however there were no significant
changes in the number of families or SIGNAL scores at these sites. It is not surprising
that the observed changes were greatest at site one, as it was most degraded site at the
beginning of the study so had the greatest scope for improvement. Sites 3 and 4 may
have showed less change than site 1, as they are downstream of the confluence with
Snowy Creek. This tributary may play an important role in providing propagules to
these sites. Alternatively, the decreased benefit for macroinvertebrates at sites 3 and 4
may be because the flood peak attenuates as it moves downstream and was shown to
decrease the scouring of cobble at more downstream sites (see section 6).
There was a different macroinvertebrate assemblage and fewer macroinvertebrate
families and individuals in newly inundated cobble than in permanently inundated
cobble on day two of the second variable flow release (date 2). However, by day 8 of
the third variable flow (date 6) there was a similar macroinvertebrate assemblage and
a similar number of families and individuals in the newly inundated cobble to the
permanently inundated cobble. This suggests that newly inundated cobble provides
suitable habitat for macroinvertebrates and that they were able to colonise this habitat
over time. The cumulative effect of the variable flow releases on the
macroinvertebrate assemblage parallels that observed in the biofilm in littoral areas
(section 6), which continued to develop over time despite being dried between the
individual variable flow releases.
Despite the fact that there was a similar macroinvertebrate assemblage and a similar
number of families and individuals in the newly inundated cobble by the end of the
third variable flow release (date 6), the SIGNAL scores in newly inundated cobble
were lower or identical to that in permanently inundated cobble on all four sample
dates (2, 3, 5 and 6). This suggests that while there are many macroinvertebrate
families colonising the newly inundated cobble, some of the sensitive taxa have not
colonised this habitat by the end of a third variable flow release.
The 37 days of constant flows following the CRP produced different responses of
macroinvertebrates at different sites. At site one there was no significant change in the
number of families or individuals, however there was an increase in SIGNAL score.
In contrast, at sites two and three there were significant increases in number of
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
104
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
families, increased abundance of tolerant families such as Chironomidae and
Oligochaeta and decreased abundance of more sensitive families such as
Coloburiscidae. Thus, the more sensitive families were colonising the cobble habitat
at site one during the period of constant flows however the more tolerant taxa were
increasing in abundance at sites further downstream. The reduced level scouring of
the biofilm at sites 3 and 4 relative to site one (see section 6) means there was less
change in the biofilm community during the CRP at these sites relative to site one.
Thus it is possible that the benefits of the CRP were still being realised at site 1 during
the constant flow period.
7.5
•
Summary of findings
The implementation of the CRP to the Mitta Mitta River resulted in significant
changes in the macroinvertebrate community, with the greatest effects being
observed at the most upstream site (site 1). Macroinvertebrate indices responded
relatively rapidly to the variable flow releases. Significant responses to the flows
were detectable by 14 days after the beginning of the second variable flow release.
Although the full extent of the response to the CRP could not be determined by
this study (due to the lack of sampling prior to the CRP), this study has
demonstrated that it is possible to detect a response of macroinvertebrates to CRP.
•
Site one had fewer families and lower SIGNAL scores than other sites, which is
consistent with the findings of a previous study by AWT (2000) in this river.
•
The greatest effect of the CRP was observed at site one, where there was a
significant increase in macroinvertebrate families, a significant change in
community composition and a substantial increase in SIGNAL scores in
permanently inundated cobble by the end of the third variable flow release. There
was no change in the number of families or community assemblage in Snowy
Creek during the period when variable flows were released in the Mitta Mitta
River.
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
105
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
•
The newly inundated cobble provided suitable habitat for macroinvertebrates and
was colonised by more families during the third variable flow release than during
the second variable flow release, suggesting there is a cumulative effect of the
flows. The macroinvertebrate assemblage in the newly inundated cobble became
more similar to the permanently inundated cobble over time.
•
The 37 days of constant flows following the CRP produced different responses of
macroinvertebrates at different sites. At site one the SIGNAL score for the
macroinvertebrate assemblage increased during the 37 days of constant flows. In
contrast, at sites two and three there were significant increases in number of
families, increased abundance of tolerant families and decreased abundance of
more sensitive families.
•
The numbers of families in littoral habitats varied considerably between sample
dates at all sites, including the reference site. This suggests that the qualitative
sweep method used to sample littoral habitats is not as reliable for the assessment
of the CRP as the quantitative surber method used in the cobble habitat.
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
106
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
8.0 SUMMARY & RECOMMENDATIONS
8.1 Effects of variable flow releases on the ecological
condition of the Mitta Mitta River
Table 8.1 summarises the response of different parameters to the variable flow
releases from Dartmouth Dam to the Mitta Mitta River. Variable flow releases from
Dartmouth Dam to the Mitta Mitta River led to substantial changes in the water
quality and biotic parameters measured in this study. In contrast, over the same period
of time there was generally no change in the parameters measured at the reference site
Snowy Creek.
The water quality in the Mitta Mitta River during the CRP differed from that during
the 37 days of constant low flows. There was lower conductivity, pH and temperature,
and higher POM, TSS and water column Chl-a in the Mitta Mitta River during the
CRP than during the constant low flow period.
There was a slight decrease in the biomass of biofilms following the CRP in the Mitta
Mitta River. This coincided with increased activity of some major water column
bacterial enzymes, changed composition of biofilm algal species and rapid changes in
net productivity at all four sites in the Mitta Mitta River. These data suggest that the
variable flow releases scoured algal biofilms from cobble substrata at all sites along
the Mitta Mitta River. The scouring of the biofilm from the cobble substrata appears
to have triggered a response of bacteria in the water column and changed the
community composition of biofilms by removing filamentous green and blue-green
algae and increasing the relative biovolume of early successional species of diatoms.
The response of macroinvertebrates was more pronounced at site one than at the other
sites in the Mitta Mitta River. There was an increased number of families and
increased SIGNAL scores at site one only, however there were significant changes in
community composition of macroinvertebrates at three of the four sites in the Mitta
Mitta River. These changes in community composition may have been a response to
the changed composition of the biofilm algal species.
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
107
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
Table 8.1 Summary of effects of the CRP on chemical and biological parameters in the Mitta Mitta River and Snowy Creek.
= increase,
= decrease,
community composition changed, - = no change in parameter, no data = no data for this parameter at this site.
Water quality
Water column extracellular enzymes
Biofilm structure and function
Macroinvertebrates
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
Parameter
DOC
POM
Water column Chlorophyll
Total suspended solids
nutrients
temperature
conductivity
Dissolved oxygen
pH
α-glucoside (carbohydrate)
β-glucoside (carbohydrate)
Butyrate (fatty acid)
Leucine (aminopeptidase)
Xyloside (woody substrate)
Total biomass (dry weight)
Organic biomass (ash free dry weight)
Algal biomass (chlorophyll a)
Biofilm taxonomy
Biofilm metabolism
Diversity of families
Number of individuals
SIGNAL scores
Community composition
Mitta Mitta River
Site 1
Site 2
-
Site 3
-
Site 4
-
-
-
No data
No data
No data
No data
No data
No data
No data
No data
108
-
-
-
-
-
Site 5 (ref)
No data
No data
No data
No data
-
No data
No data
-
No data
No data
-
-
No data
No data
-
=
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
8.2 Effects of 37 days constant and low flows on the
ecological condition of the Mitta Mitta River
Table 8.2 summarises the response of different parameters to the 37 days of low and
constant flows that followed the CRP in the Mitta Mitta River. Many water quality
and biotic parameters displayed substantial changes during the 37 days of low and
constant flows that followed the successive variable flow releases in the Mitta Mitta
River. In contrast, over the same period there was no change in most of the parameters
measured at the reference site in Snowy Creek.
Water quality in the Mitta Mitta River changed substantially during the low flow
period. During this period there was an increase in temperature and conductivity and a
decrease in TSS and POM.
The biomass of biofilms increased during the constant flow period in the Mitta Mitta
River. This coincided with very low activity of water column bacteria, changed
composition of biofilm algal species and decreased net productivity to a point where
biofilms at site 4 were net consumers of oxygen by the end of this period. During the
constant flow period there was no scouring of biofilm from cobble substrata and the
composition of the biofilm at site four changed from one dominated by diatoms and
green algae to one dominated by only two species of filamentous blue-green algae.
The response of macroinvertebrates to the constant flows differed between sites. At
site one there was no change in the number of families but the SIGNAL score
continued to increase, suggesting that the more sensitive families were continuing to
colonise the cobble and any ecological effects of the CRP at this site were still being
realised. In contrast, there was a decrease in the SIGNAL score at site two and
increased abundance of tolerant families such as Chironomidae and Oligochaeta and
decreased abundance of more sensitive families such as Coloburiscidae at sites two
and three by the end of the constant flow period. It is possible that any ecological
effects of the CRP are more short-lived at sites two, three and four when compared to
site one.
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
Table 8.2 Summary of effects of 37 days of constant flows on chemical and biological parameters in the Mitta Mitta River and Snowy Creek.
= decrease, = community composition changed, - = no change in parameter, no data = no data for this parameter at this site.
Water quality
Water column extracellular enzymes
Biofilm structure and function
Macroinvertebrates
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
Parameter
DOC
POM
Water column Chlorophyll
Total suspended solids
nutrients
temperature
conductivity
Dissolved oxygen
pH
α-glucoside (carbohydrate)
β-glucoside (carbohydrate)
Butyrate (fatty acid)
Leucine (aminopeptidase)
Xyloside (woody substrate)
Total biomass (dry weight)
Organic biomass (ash free dry weight)
Algal biomass (chlorophyll a)
Biofilm taxonomy
Biofilm metabolism
Diversity of families
Number of individuals
SIGNAL scores
Community composition
Mitta Mitta River
Site 1
Site 2
-
-
Site 3
-
No data
No data
No data
No data
-
No data
No data
No data
No data
-
No data
No data
No data
No data
-
-
110
Site 4
-
Site 5 (ref)
-
-
-
-
No data
No data
No data
No data
No data
No data
-
-
-
= increase,
-
Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
8.3
Recommendations for future monitoring programs
• The second and third releases produced substantial changes to the water quality
and biotic parameters measured in the Mitta Mitta River. It is possible that some
ecological changes may have also occurred during the first release, however due
to the timing of the call for tenders no samples could be collected in the period
prior to, or during the first release. This limited the ability of this study to assess
the full ecological impact of the CRP.
Recommendation 1: Future assessments of CRP’s should include at least two sample
dates prior to the first release, followed by two sample dates during each subsequent
release and several samples dates during the constant period of flows following the
end of the release pattern.
• The results suggested that long periods of low and constant flows substantially
alters the ecological condition of the river system, however the current study was
not structured to identify the critical threshold point at which constant flows
become detrimental.
Recommendation 2: Future assessments of CRP’s should include a detailed study of
the period of constant flows prior to and following the release period to identify
thresholds at which constant flows become detrimental and at which point CRP’s
should be introduced.
•
This research demonstrated very short-term responses of enzyme activity during
peak flows with minimal changes in activity under constant flow conditions.
Recommendation 3: Future CRP’s in the Mitta Mitta River downstream of Dartmouth
Dam require flood peaks of at least 4800ML/day (at Colemans gauge) to maximise
rates of microbial productivity for a diverse range of water column bacteria. Future
monitoring can target resources at specific flow events to streamline sample collection
and minimise costs.
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
•
Structural and functional responses of biofilms were evident immediately
following the peak flows of each variable flow release, as well integrating
responses to flow regime over longer time periods. This suggests the biofilm
attributes and the temporal scale of their measurement used in this study are
appropriate for monitoring changes in the ecological condition of the Mitta Mitta
River.
Recommendation 4: Future assessments of CRP’s should include all the biofilm
attributes sampled to provide a range of structural and functional responses of
ecological communities to variable flow releases. Increased replication may reduce
the large variances found in some attributes and help better identify significant
changes in biofilm assemblages.
• The collection of four replicate water samples at each site on each sampling date
to determine extracellular enzyme activity from the water column provided
minimal statistical power to test hypotheses and examine the significant effects of
the CRP’s on microbial productivity.
Recommendation 5: Replication of this parameter should be increased to improve the
power of the statistical analyses. The suite of enzymes examined represent a range of
naturally occurring carbon sources and should be retained in future monitoring
programs.
• Several macroinvertebrate attributes measured in cobble habitats (number of
families, SIGNAL scores and community composition) responded relatively
rapidly to the variable flow releases. The four quantitative surber replicates taken
from cobble habitats at each site on each sampling date provided sufficient
statistical power to detect significant effects of the release pattern. This suggests
that the attributes and temporal scale of measurement used in this study are
appropriate for future monitoring programs.
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
Recommendation 6: Future assessments of CRP’s should include a minimum of four
surber sample replicates of cobble habitat per site per sample date to allow ANOSIM
analyses to be performed to detect significant differences in community composition
between sample dates. Both abundance and diversity of macroinvertebrates should be
measured.
•
The variability in numbers of families in the littoral habitat at all sites, including
the reference site in Snowy Creek, suggests that factors other than flow may
influence this parameter and it may not be as reliable as the quantitative
assessment of cobble habitat for the assessment of CRP’s.
Recommendation 7: Future assessments of CRP’s should carefully consider the costbenefits of including the qualitative sweep method in the monitoring program.
JOHNSTONE CENTRE - CHARLES STURT UNIVERSITY
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
APPENDIX 1
PROJECT BREIF
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
Call for Tenders
Variable Releases from Dartmouth Dam
River Murray Water (RMW) propose to trial variable releases from Dartmouth Dam over
the period late-November to late-December 2001. The background and details of this
proposed release pattern are contained in the attached letter from RMW (dated 14 November
2001).
The Commission has been provided with a draft study brief by Dr Terry Hillman, Member
of the Expert Reference Panel on Environmental Flows and the Independent Sustainable
River Audit Group (ISRAG), and this is also attached.
Further, a letter to RMW from the North East CMA (John Riddiford) commenting on the
proposal is attached as background. Please note that this letter should be treated as
commercial-in-confidence correspondence between NECMA and RMW and is to be used
only in the preparation, and if successful, execution of this work.
Tenders
Tenders are invited from suitably qualified suppliers to perform monitoring in the Mitta
Mitta Valley during November and December 2001. Tenders will define a proposed
sampling program consistent with the draft study brief prepared by Dr Hillman, and may
include further work with appropriate justification. Geomorpholocigal issues may also be
consuideredn in this program.
Please allow in your tender for provision of a full report on the monitoring including
recommendations for future monitoring of such events in the Mitta Mitta River.
While the planned releases are detailed in the attached documentation, such releases can be
changed significantly in response to weather conditions. Accordingly please include the
basis for variations in contract arrangements. Please advise by close of business Monday 19
November 2001 of your intention, or otherwise, to proceed with a tender. Tenders are
welcome as soon as practicable.
Contacts
Tony McLeod, Environmental Flows, 02 6279 0127 0409 908 015
Brian Lawrence, Manager Riverine, 02 6279 0160
Bruce Campbell, River Murray Water, 02 6279 0169
________________________________
Tony McLeod
Murray-Darling Basin Commission
GPO Box 409, Canberra ACT 2601
Tel: 02 6279 0127 Fax: 02 6248 8053
Mobile: 0409 908 015
Email: [email protected]
Web Page: www.mdbc.gov.au ________________________________
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
10 November 20051
Mac Paton
Chairperson
Mitta Mitta Water Services Committee
RMB 1135
Tallangattta Vic 3700
Fax (02) 6071 7260
Dear Mac
Proposal for Pattern of Variable Release from Dartmouth Dam
We are writing to seek your comments regarding a proposal to introduce a cycle of variation
in the release rate from Dartmouth Dam for environmental benefit.
For your background, harmony releases at Colemans have been maintained at 4 000 ML/day
since 18 October 2001. This is despite the fact that harmony transfer rules show that based
on current storage levels in both Dartmouth and Hume Reservoirs, the calculated harmony
transfer volume for November would require releases at close to channel capacity in
November, with relatively little volume transferred in December.
However, River Murray Water, in consultation with Goulburn-Murray Water and the North
East Catchment Management Authority, has determined that in the current circumstances, it
would be more appropriate to average the harmony transfers in November and December.
This is expected to reduce the potential for erosion caused by higher flow rates.
With this in mind, River Murray Water presently estimates that the current requirements for
transfer to Hume will be maintained until about the end of December, however, if wetter
conditions occur in the Murray catchment, a lower average rate of transfer may be required.
In addition to this, rather than continuing to release at a constant rate over the next several
weeks, it is proposed that a minor flow “pulse” be trialed to simulate a natural rainfall event.
This variable flow pattern is consistent with the recommendations of the Commission’s
River Murray Scientific Panel on Environmental Flows1. The proposed cycling of flow
includes a variation in water level of about 0.25 m at Colemans and 0.25 at Tallandoon (see
Attachment A). The size of the proposed variation is similar to what may occur during
power station entitlement releases, or which occur during natural flow events in tributaries
downstream of Dartmouth.
The trial flow pattern is expected to benefit riparian vegetation and biofilms in the riparian
zone, fish migration, and reduce the impact of erosion caused by constant water levels. The
MDBC Natural Resources section is arranging for some monitoring to be undertaken to
gauge the environmental response to the trial.
This proposal is not expected to cause inconvenience to diverters along the lower Mitta
Mitta River. However, diverters are advised that the flow rises could increase leaf litter and
other debris. Flow rises will be timed to take place during the week to reduce the potential
for these problems, as well as providing some small benefit to electricity generation.
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
If the Water Services Committee has any concerns regarding the proposed trial, please
contact Bruce Campbell, River Management Engineer, on 02 6279 0100 by 18 November
2001.
River Murray Water is intending to issue a media release late this week confirming
arrangements if no significant obstacles are identified.
If there is no initial concern regarding this trial, we will also seek feedback from landholders
via the Water Service Committee after any trial is carried out.
Yours sincerely
David Dole
General Manager
1
Thoms, M. C., Suter, P., Roberts, J., Koehn, J., Jones, G., Hillman, T. and Close, A., 2000. Report of the
River Murray Scientific Panel on Environmental Flows: River Murray - Dartmouth to Wellington and the
Lower Darling River. Scientific Panel on Environmental Flows, Murray-Darling Basin Commission, Canberra,
June 2000.
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Attachment A
Dartmouth Release – Trial Flow and Water Level Pattern
November/December 2001
The trial flow “pulse” is proposed on the following basis:Duration of each pulse cycle 14
days
Flow Rise 2
days
Flow Recession 12
days
First
pulse
proposed
to
commence
Week commencing 19/11/01
Colemans Gauge
Average
flow
Maximum
Minimum
Average
Water
Water
Level
Level
required
4 000 ML/day
Flow
4 800 ML/day
Flow
3 200 ML/day
(Colemans
gauge)
2.08 m
Variation
0.25 m total
Tallandoon Gauge *
Average
Maximum
Minimum
Average
Water
Water
Level
Level
flow
5 000 ML/day
Flow
5 800 ML/day
Flow
4 200 ML/day
(Tallandoon
gauge)
2.43 m
Variation
0.25 m total
* Assumes constant inflows of 1 000 ML/day from Snowy Creek and other minor
tributaries. These flows may be slightly higher if there is significant rainfall.
If the variation on flow coincides with a significant flush caused by inflows from tributaries
downstream of Dartmouth, the program may be modified to prevent inconvenience to
diverters.
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
November 2001
Mr Bruce Campbell
River Management Engineer
River Murray Water
GPO Box 409
Canberra ACT 2601
Dear Bruce
Re
:
Dartmouth operations season 2001/2002
Thank you for your fax dated 11 October 2001 requesting comments on the water transfer
from Dartmouth Dam. In general, the CMA supports the proposed program during
spring/early summer of 2001 because it creates the opportunity to periodically inundate
areas of the Mitta Mitta riparian zone for the benefit of wetland ecology. However, I qualify
my support with the following comments and recommendations.
a) The Harmony program is essentially a form of 'pre-release' strategy that aims to
minimise the chance of physical spill from Dartmouth storage. As such, the program
does not benefit the floodplain on ecological grounds because it minimises floodplain
inundation (as also stated by the River Murray Expert Panel for Environmental Flows,
2000).
b) However, given that the chance of spill is very low in both storages (currently around
10%), then the alternative is for 'normal' transfer rules to be maintained that causes
constant in-channel flow rates to be passed from Dartmouth Dam.
The disadvantage of constant flow rates have been highlighted by the Expert Panel as
causing:
- Loss of stimulation for fish movements;
- Reduction in the range of riverbank habitat and bed habitat (i.e., reduced wet/dry area);
- Instability of the river channel banks and subsequent reduction of in-channel
complexity and habitat diversity due to erosion and sedimentation.
The basis of the current RMW proposal is to fluctuate the rate of the transfers to cause
variability in Mitta Mitta River running levels. Given this being the alternative to stable
transfer rates, then the opportunity for variable transfer rates is supported.
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c) However, concern exists for low water temperature arising from Dartmouth release
being inappropriate for native fish breeding response or success, and reducing other
biological response. Variable water flow management may instead be generally more
beneficial to improved riparian habitat and diversity, with native fish benefiting only
from anticipated improved food resource being washed and transferred into the lower
river systems.
d) In releasing variable flow rates, the following hydrograph and associated issues are
recommended:
- Aim for cycle of 2 peaks per month (though four per month, as may be preferred by
the power station, could instead be accommodated, though remains NECMA's
secondary preference);
- Have rapid rise followed by slower recession;
- Current proposal is fluctuation within river channel capacity. Explore options to
increase flow rates within this range that will connect the river to adjoining
anabranches, backwaters and associated floodplain wetland depressions;
- Have greatest flows in October/November, decreasing in December, so as to more
closely emulate natural hydrograph. However, having said this, it may be pertinent
to shift the hydrograph by a month to assist in alleviating impact of cold water
pollution (reservoir thermal effect).
- That significant flow pulses in Snowy Creek be reflected as a flow pulse down the
Mitta Mitta River to Hume Dam.
e) Implement a monitoring program to validate the effectiveness of variable flow
management in the Mitta Mitta River. At a minimum, monitoring should include:
- Hydrographic monitoring (i.e., to record river running height variations);
- Basic mapping (recording) of inundation extent (especially sites where water escapes
from the main river channel);
- Basic phys-chemical properties (i.e., pH, temperature, turbidity, conductivity, D.O.,
etc);
- Basic survey of flora response (i.e., general growth and flowering).
Plus, where possible, include more detailed, scientifically defensible, monitoring such
as:
- Biofilm development and fate through literal zone;
- Fish movement and breeding success;
- Flora response between sites (e.g., billabongs) that have been influenced by
increased frequency of flood fluctuations compared to sites without;
- Invertebrate response;
- Amphibian response;
- Waterbird response;
- Carbon cycling.
f) The regulated flow rate of ≤5,000 ML/day should be targeted whenever possible to
prevent the long-term saturation of the upper bank caused by the bank full-regulated
flow of 10,000 ML/day.
- When River Murray Water is required to exceed 5,000 ML/day to meet water
transfer demands, flow releases up to 10,000 ML/day can be used. Releases up to
10,000 ML/day must be designed to mitigate impacts associated with the long-term
saturation of the upper bank.
- When dropping flow rates from 10,000 to 5,000 ML/day, it is important that
drawdown rates do not exceed those that would have occurred naturally after similar
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periods of bank full flow. That is, the longer flows are held at bank full, the slower
the drawdown rate needs to be to mimic natural. For example, if a transfer is held at
10,000 ML/d for 1 month then the drawdown rate between 10,000 and 5,000 ML/d
should be no greater than that recorded from a historical flood event that exceeded
10,000 ML/d for 1 month. In this way the transfer “event” is matched as closely as
possible to a “natural” flood event. However, it needs to be noted that if the
frequency of bankfull flow events of a specified duration exceeds the natural
frequency, elevated erosion rates may occur simply due to increased event frequency
(i.e. natural drawdown rates are likely to be associated with some erosion, and
increased frequency means an increase in this erosion).
If you require further information please contact Mr Keith Ward on (03) 58 335 947.
Yours sincerely
John Riddiford
Chief Executive Officer
CC
Keith Ward, Dean Judd
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Flow Manipulation in Mitta Mitta River Nov – Dec 2001
NOTES FOR DRAFT STUDY BRIEF
Introduction:
• Releases are to be made from Dartmouth Dam during November – December to
augment storage in Lake Hume (in line with harmony rules).
• The Murray Darling Basin Commission has decided to make these releases on a
variable flow pattern (2 days rise / 12 days fall) and is seeking assistance in assessing
the ecological effects of this modification to management practice.
• It is recognised that, because of the timing and lack of opportunity, this study will be
exploratory in nature and the Commission therefore intends that the work undertaken
will:
Identify components of the ecosystem which might be expected to respond to a
change from constant to variable flow patterns on the proposed scale.
Provide measurements indicative of that response
Form the basis for preliminary assessment and advice for management of
variable releases
Provide data and insights which could support and help direct more rigorous
studies in the future.
Components of the Ecosystem to be Assessed
Given the time constraints and scale of release the following components of the Mitta Mitta
ecosystem have been identified for assessment.
WATER QUALITY: Periodic changes in water level may be expected to result in
corresponding changes in water quality from a variety of potential causes – wetting/drying,
movement to and from riparian zones, resuspension etc. A range of appropriate WQ
parameters should be monitored with sufficient intensity to estimate ‘end-of-valley’ effects
of the flow manipulation.
RIVER PRODUCTIVITY: Short-term variation may influence the rate of photosynthetic
production and the relative significance of various primary producers (ie the biodiversity of
primary producers). Under the current circumstances, the following observations should be
carried out with the desired outcome being measurement of cyclic changes in
production/respiration in the river system and indications of areas requiring more intensive
study.
1. Biofilm Composition. Static and floating glass-slide samplers exposed to detect
effects of flow variation on species diversity and biomass.
2. Benthic production/respiration. Estimations of P/R ratios in wet/dry benthic zones.
3. Water Column Production. Companion measurements to 1 and 2 above on water
column phytoplankton. Aimed at estimating likely changes to the relative
contribution (and therefore diversity) of benthic and water column organisms in
providing organic carbon to the river system.
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4. [ The use of enzyme activity measurements to quantify bacterial activity is also a
possibility but I have not been able to assess the relative effort/ payoff or the likely
sensitivity to flow fluctuations]
INVERTEBRATES: Observations on invertebrates should address two major questions – Does
flow variation stimulate interaction with riparian/floodplain aquatic systems, and, does
wetting and drying of in-stream benches change the diversity of macroinvertebrates, increase
drift (and therefore mixing, colonization etc) with an overall positive or negative effect on
the macroinvertebrate community of the Mitta Mitta.
• Under the present conditions a detailed study of microinvertebrates is not warranted.
The deployment of drift nets along the river (see ‘fish’ below also), to cover the
range of flow events, and provide the basis for assessing riparian/floodplain inputs is
suggested.
• Comparative samples of benthic macroinvertebrates on permanently inundated and
cyclically inundated benches again would provide indicative information regarding
the likely effects of variable flow.
FISH: The scale, lack of ‘before’ data and/or controls limits the possible value of fish
observations. The time of year (post breeding for many of the major species) and
significantly changed water temperature further limits the ability to compare observations
with other experience. Two sets of observations should be included in this program:
• Use of drift-net catches from Macroinvertebrate survey. If (perhaps because of
temperature depression) Murray Cod are breeding drift-net samples may link drift of
larval cod to flow pattern providing a basis for further work
• Recent indications that European Carp may be trapped into breeding in highly
impermanent waters provides an opportunity for an observational study on
backwaters and small riparian waterbodies on the Mitta Mitta during the variable
release program. Contribution to Carp control might be incorporated into designing
variable flow patterns if a response can be measured during this trial.
Dr Terry Hillman
14 November 2001
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APPENDIX 2
JOHNSTONE CENTRE PROPOSAL
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JOHNSTONE CENTRE
RESEARCH IN NATURAL RESOURCES & SOCIETY
Environmental Consulting
Quote No.0047
Ecological Assessment of Variable Flow Releases in the
Mitta Mitta River
MDBC
___________
Wagga Wagga 2001
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1.0 INTRODUCTION
Current ecosystem management to restore river health in most of the Murray-Darling Basin
focuses on providing ‘environmental flows’ from upstream water storages (e.g. EPA 1997).
Environmental releases attempt to mimic natural flow variability in regulated rivers and
drive ecological processes necessary for river rehabilitation.
River Murray Water (RMW) proposes to trial variable releases from Dartmouth Dam into
the Mitta Mitta River during November and December 2001. The Murray Darling Basin
Commission (MDBC) has decided to make these releases on a variable flow pattern (2 day
rises / 12 days fall) and is seeking assistance in assessing the ecological effects of this
modification to management practice.
This document details a proposal by the Johnstone Centre to undertake the ecological
assessment of variable flow releases in the Mitta Mitta River.
2.0 JOHNSTONE
UNIVERSITY
2.1
CENTRE,
CHARLES
STURT
CENTRE PROFILE
The Johnstone Centre is one of five research centres at Charles Sturt University. The Centre
is made up of academics, postgraduate students, consulting staff and support staff. The
Johnstone Centre’s mission is to research the fundamental ecological processes involved in
the conservation of the diverse range of ecosystems and protected areas in Australia and
overseas, crucial to their successful management.
Our research contributes to developing a greater understanding of ecological processes on a
community and landscape scale and applies the results of such research to challenge current
practices, policies and planning. These studies enable us to establish the conditions
necessary for ecologically sound management, as well as biodiversity assessment and
conservation evaluation.
Johnstone Centre - Environmental Consulting and associated academics from Charles Sturt
University have worked extensively in the MDB and beyond, with research focused on
natural resource management, target survey and management in agricultural systems. Recent
projects related to the study of artificial flow variation include ‘Assessment of
Environmental Flows for the Murrumbidgee River: Developing biological indicators for
assessing river flow management’.
2.2
Assessment of Environmental Flows for the Murrumbidgee River
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Dr Robyn Watts et al. (2001) from Charles Sturt University have recently completed the
development and assessment of biological indicators for the assessment of environmental
flows in the Murrumbidgee River and associated tributaries. Head water tributaries such as
the Tumut, Goodradigbee and Goobagandra Rivers were included in this study which
analysed the response of indicator species of macroinvertebrates and biofilm metabolism to
changes in flow management. A copy of the CD-ROM of this project can be obtained by
contacting Dr Robyn Watts on 02 69332329.
The Goodradigbee and Goobagandra Rivers are very similar geomorphically, have similar
substrata and are cold water streams like Snowy Creek and Little Snowy Creek. The Tumut
River is quite similar in many respects to the Mitta Mitta River, in respect to it being
downstream of Blowering Dam and having similar substrata and hydrological regimes.
The experience, expertise and equipment available to the Environmental Flows Assessment
team at Charles Sturt University makes them highly capable of assessing the variable
releases proposed for the Mitta Mitta River.
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2.0
METHODS
2.1
SITE SELECTION
A recognisance trip will be made to the Mitta Mitta River one week prior to the
commencement of sampling to confirm sampling sites. At present four sampling sites have
been confirmed and an two extra sites is being considered. Sites 1, 2, 3 and 5 are at the same
location as Sites 502, 505, 503 and 504 as used for the Mitta Mitta River Biological
Monitoring Program, respectively (AWT Victoria 2000). Sites 4 and 6 are to be located
upon Little Snowy Creek u/s of the Mitta Mitta confluence and a site downstream of the
Tallandoon gauge, respectively.
2.2
WATER QUALITY (WQ)
Water quality parameters to be measured include; Dissolved Organic Carbon (DOC),
Particulate Organic Carbon (POC), Suspended Solids (SS), Conductivity (Cond),
Temperature (temp), Turbidity (turb), DO (mg/L), velocity, light intensity, water column
chlorophyll.
Water samples will be taken from each of the six sites following the proposed sampling
regime (Table 5). At each sampling site and on each sampling day, five filtered water
samples (300mL) will be collected. These samples will be analysed in the laboratory for
DOC, POC, SS and water column chlorophyll. The remaining water quality parameters will
be recorded on site using a multimeter and flow meter.
Three additional samples (30mL) will also be collected for the analysis of Total Phosphorus
(TP), Total Nitrogen (TN) and ortho Phosphate.
2.3
RIVER PRODUCTIVITY
2.3.1 Biofilm Composition
The project team have recommended the use of cobble stones for the analysis of biofilm
composition, as apposed to static and floating glass slides. Artificial growing strata such as
glass slides act as a reference that are used to gauge the response of biofilms to changes in
flow regime. Given that the 1st variable release has started, colonising biofilms would
represent a community composition that developed during variable conditions.
We propose to use cobbles in the existing substrata as a guide to biofilm composition prior
to variable flow release. The project will then assess biofilm response to changes in flow
regime over a forty day period following the return to constant conditions.
Cobbles will be removed from the water column at two different depths, deep and newly
inundated. Two cobbles will be removed at each depth, one will be placed in a cold box at 4
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degrees C and taken to the laboratory for live identification and one will be scrubbed and the
biofilm will be preserved in alcohol. This process will be conducted upon day 0, 2, 8 and 14
during both variable flow periods and then every ten days for forty days following the return
to constant river heights. Sampling of biofilm composition will occur at each of the six study
zones. Sampling will be conduced on days 0 and 2 to gauge the response of biofilms to
scouring.
Dr Adrienne Burns will complete the biofilm identifications to the lowest taxonomic
resolution possible.
2.3.2 Benthic metabolism
Benthic metabolism will be measured at sampling sites 3 and 6. Eight chambers described
below will be available at each site during each sampling period and will be placed on racks
and held in the water column of the Mitta Mitta River. Four randomly selected cobbles (of
suitable size) will be removed from the river and placed into a chamber for a period of 24
hours. During this period an Orion 835A DO datalogger will monitor changes in DO
concentration (mgL -1 ) within the chamber at 8 minute intervals. Sampling will be
conducted on the day prior to variable flow event 2 and then every 24 hours over the first
three days of variable flow release. Metabolism of biofilms will then be assessed on day
eight and day 14 for release periods 2 and 3, then every ten days for forty days following
day 14 of the 3rd variable flow period.
A new cobble will be selected within the same area for each 24 hour assessment. At the
completion of the incubation, each block will be removed and sealed in a plastic bag for
determination of organic and inorganic biomass.
Chambers have been specifically designed for biofilm metabolism assessment. Each
chamber consists of a 20cm length of 20cm inner diameter clear Perspex tubing (with a
volume of 4L) and two end caps made of clear perspex. Cobbles will be held in place using
a nylon screw into a perspex pedestal attached to the base of the chamber that centred the
block horizontally. Water is recirculated within each chamber using a variable speed,
submersible 12V pump located on the outside of the chamber and connected to each end cap
using nylon tubing. Recirculated water entered the chamber through an outlet that disperses
water evenly across the block surface and was directed across the chamber to the
recirculating pump inlet valve on the other end cap. This simulates the direction and velocity
of flow experienced by in situ biofilms by varying the speed of the recirculating pumps. A
bilge pump located at the base of one end cap vented the contents of the chamber every 90
minutes. At the top of the other end cap, a one way valve allows the chambers to be refilled
with river water via the pressure created from the bilge pump operation. A port in the end
cap allowed an Orion 08310A DO probe to be positioned 3cm above the horizontal surface
of the colonised block.
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At each sampling date, underwater irradiance (_E/cm/sec) will be measured at 15 minute
intervals for a minimum of 24 hours at 15cm below the surface using a LICOR LI-92SA
Underwater Quantum Sensor attached to a 6004-21 Starlogger System. Water temperature
will be recorded by an Orion 835A DO datalogger at 8 minute intervals for the 24 hour
incubation. Water column pH and conductivity are to be taken at 15cm depth below the
water surface using a Yeo-Kal muliprobe meter at 0, 12 and 24 hour time intervals. Water
samples (500mL) will also be taken from 15cm below the water surface at 0, 12 and 24 hour
time and filtered through a pre-weighed GFF filter paper, dried at 80°C for 48 hours and
reweighed to determine Total Suspended Solids (TSS) in mg/L.
2.3.3 Water Column Metbolism
Water column metabolism will be assessed using Perspex chambers with no cobbles inside.
During the benthic metabolism sampling periods the remaining four chambers at each site
will be used to measure water column metbolism. River water is pumped through each
chamber and the Orion datalogger will record DO concentration at 8 minute intervals for a
period of 24 hours. Water column production will be measured at the same times as the
benthic metabolism.
2.3.4 Enzyme Activity
Five enzymes including; Butyrate, Alpha and Beta glucoside, Beta xyloside and Leucine
will be analysed during the assessment project. These enzymes are involved in the
degradation of polysccharides, fatty acids and proteins derived from a range of carbon
sources in rivers.
Enzyme activity will be assessed at each site, on days 0, 1, 2, 8 and 14 during both variable
flow periods 2 and 3, and then every ten days for forty days following to resumption of
constant flows. Because of the rapid response of enzyme activity to changes in flow, water
samples will be taken every 12 hours during the 1st 2 days of variable flow release.
A 30mL vial of river water will be taken at each sampling site on each of the sampling times
noted above.
The analysis of enzyme activity is an expensive process, however at present Dr Darren
Ryder is analysing enzyme activity for another project. It is suggested that samples collected
during this assessment could be piggy backed onto these samples for analysis and thus
reduce the overall price.
2.3
MACROINVERTEBRATES
Macroinvertebrates will be sampled according to the National Protocol defined in the River
Bioassessment Manual (MRHI 1994). And in the EPA (1998) publication on Rapid
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Bioassessment of Victorian Streams. The widest possible diversity of macroinvertebrates
will be assessed by sampling both the riffle and littoral habitats. All sampling will use ISO
DIS/7828 250um mesh nets (ISO 1983). Nets will be washed thoroughly between sampling
events to prevent cross contamination of samples. Sampling will be conducted using the
following methods (Section 2.3.1 and 2.3.2). Sampling will be conducted at each of the six
study sites on days 0, 2, 8 and 14 of each of the two variable flow periods and then every ten
days for a forty day period following the return to constant flow conditions.
2.3.1 Littoral Habitats
Littoral areas will be sampled using sweep nets in shallow areas with little or no current.
Vigorous sweeping techniques that disturb the substrate sufficiently to suspend benthic
animals will be employed. The nets will be swept through any vegetation, snags and logs in
backwaters. This method will be carried out over a random ten metre section at each site.
Net contents will then be emptied into white sorting trays and animals will be collected
using forceps for a period of 30 minutes. Wide-mouthed pipettes will be used to handle
fragile animals. Collected invertebrates will be preserved in 70% ethanol and identified in
the laboratory.
2.3.2 Riffle Habitats
Riffle habitats will be sampled using a 250µm mesh kick net held perpendicular to the
substrate with its opening facing upstream. Sampling will start at the downstream end of the
riffle, the streambed directly upstream of the net will be disturbed by kicking and agitating
the stones. This method will continue over ten metres, working upstream against the flow.
Net contents will be sorted in white trays, preserved and identified in the same manner as the
littoral samples.
2.3.3 Macroinvertebrate Identification
Macroinvertebrates will be identified to key families using keys listed in Hawking (2000).
Sample and identification data will be entered into a MS-Access database.
Macroinvertebrate data will be assessed using the SIGNAL-95 (Stream Invertebrate Grade
Number – Average Level) (Chessman 1995), as used by AWT Victoria (2000).
2.4
Fish
Given the small rise in water levels (~25cm) it is unexpected that the variable flow release
will trigger significant fish breeding responses. Our project team proposes to ignore a
targeted assessment of fish movement within the Mitta Mitta River during this period.
However, as part of the riffle habitat component of our proposal we intend to analyse drift
samples for fish larvae. These incidental samples will provide a coarse indication of
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breeding and may provide some useful information for future assessments within the Mitta
Mitta system.
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
3.0 BUDGET AND TIME ALLOCATION
Table 1. Summary of budget, time allocation and key personnel.
Task
Key Personal
Time Allocated
Field Work
Robyn Watts
1 day
Darren Ryder
1 day
Lachlan Sutherland
18 days
Martin Asmus
15 days
Biofilm ID
Adrienne Burns
5 days
Macroinvertebrate ID
Robyn Watts
1 day
Lachlan Sutherland
10 days
Water Quality Analysis
Lachlan Sutherland
21 hours
Enzyme Analysis
Darren Ryder
7 hours
Data Entry
Lachlan Sutherland
2 days
Data Analysis
Darren Ryder
2 days
Robyn Watts
1 day
Lachlan Sutherland
3 days
Alistar Robertson
½ day
Robyn Watts
1 day
Darren Ryder
1 day
Lachlan Sutherland
5 days
Bruce Mullins
3 days
Total Cost
Laboratory Work
Prepare and submit
assessment report
Travel
8400 km at
$0.65/km
Stationary and printing,
Sub Total
CSU Competitive Neutrality Levy**(10%)
Total (excluding GST)
GST
Total (including GST)
* The project team is committed to an entire day on site during biofilm metabolism assessments, because
of the security of equipment and monitoring the chamber pump system. Combinations of the individual
sampling programs on the same day as biofilm metabolism assessment will not incur an additional fee
because of our commitment on site.
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
** It is a legal requirement that the University charges an infrastructure levy in the interests of
competitive neutrality.
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Ecological Assessment of Cyclic Release Patterns in the Mitta Mitta River, Victoria
4.0 TIMESCALE AND WORK PLAN
The project will commence on the 2nd of December with the start of the sampling period. It
is roughly estimated that a draft assessment report will be completed by late February
(Table4). Sampling will commence on the 2nd of December, one day prior to the 2nd flood
period and continue for forty days after the last day of the 3rd flood event to the 8th of
February, 2002 (Table 5).
Table 2. Gantt Chart
Conduct sampling
Biofilm ID
Macroinvertebrate ID
Nutrient Analysis
Enzyme Analysis
Water Quality Analysis
Data Analysis
Report
Month
Dec
Jan
Feb
Table 3. Sampling regime
Date
Day Cumulative days WQ Enzyme Biofilm comp. Benthic metab.
2/12/01
0
0
3/12/01 *1
*1
4/12/01
2
2
5/12/01
3
3
6/12/01
4
4
7/12/01
5
5
8/12/01
6
6
9/12/01
7
7
10/12/01
8
8
11/12/01
9
9
12/12/01 10
10
13/12/01 11
11
14/12/01 12
12
15/12/01 13
13
16/12/01 14
14
17/12/01
1
15
18/12/01
2
16
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19/12/01
20/12/01
21/12/01
22/12/01
23/12/01
24/12/01
25/12/01
26/12/01
27/12/01
28/12/01
29/12/01
30/12/01
9/01/02
19/01/02
29/01/02
8/02/02
3
4
5
6
7
8
9
10
11
12
13
14
10
20
30
40
17
18
19
20
21
22
23
24
25
26
27
28
38
48
58
68
* Commencement of the 2nd variable release period.
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5.0 PROJECT TEAM
The project team will be comprised of:
•
Professor Alistar Robertson, BSc (Hons), PhD
•
Dr Robyn Watts, BSc (Hons), PhD
•
Dr Darren Ryder, BSc (Hons), PhD
•
Dr Adrienne Burns, BSc (Hons), PhD
•
Mr Bruce Mullins, BSc, MSc
•
Mr Lachlan Sutherland, BAppSc (Hons)
•
Mr Martin Asmus, BAppSc (Hons)
Professor Alistar Robertson
Professor Alistar Robertson is an ecologist with 22 years experience studying ecological
and geochemical processes in aquatic habitats, including trophodynamics, nutrient cycling,
fish biology and vegetation dynamics in seagrass, mangrove and freshwater wetlands in
Australia, Papua New Guinea, south east Asia and Mexico. His present research targets
include the integration of agricultural and ecological systems at a range of spatial scales.
As well as, the impact of introduced carp and domestic grazing herds on the ecology of
riparian zones and off-river waterbodies and the role of flood pulses in the ecology of
floodplain-river systems.
Dr Robyn Watts
Dr Watts’ current research at CSU is focussed on developing biological indicators of river
health for the assessment of environmental flows. Dr Robyn Watts has recently completed
a research project entitled ‘Assessment of Environmental Flows for the Murrumbidgee
River: developing biological indicators for assessing river flow management’. This work is
at the forefront of environmental flows research in Australia as we examined the
association between instream and riparian biological indicators and hydrological variables.
This work follows on from her previous studies of the population genetics of golden perch,
silver perch and eel-tailed catfish within the Murray-Darling Basin. Robyn has also
completed a consultancy project for Ok Tedi Mining Limited in Papua New Guinea,
examining the population genetics and morphological variation in two freshwater fishes,
Nematalosa flyensis and N. papuensis, from the Fly River.
Dr Darren Ryder
Dr. Ryder is an aquatic ecologist with extensive experience in the field of freshwater
ecology, specifically dealing with the microbiology/biogeochemistry of wetland and
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riverine systems. His current research at CSU as an Australian Research Council Post
Doctoral Research Fellow is focussed on developing biological indicators of river health
for the assessment of environmental flows across many NSW river systems. This research
specifically examines biofilm structure and function and the response of consumers to
changes in biofilm attributes, and builds on a previous Post Doctoral position at CSU that
developed biofilms and macroinvertebrates as biological indicators for the assessment of
environmental flows in the Murrumbidgee River. Dr. Ryder has a thorough knowledge of
riverine hydrology and instream processes and has been a member of many scientific
panels including method design team for the NSW Integrated Monitoring of
Environmental Flows and 'river health report card' committees.
Dr Adrienne Burns
Dr Burns is an aquatic ecologist with extensive experience in the field of freshwater
ecology, specifically dealing with the biogeochemistry of wetland and riverine systems.
Her current research at CSU as a Post Doctoral Research Fellow examines the role of river
floodplain interactions during high flows. Dr. Burns has an extensive background in
biofilm structure in riverine systems and has developed a thorough knowledge of
freshwater algal taxonomy through her doctoral research. Dr Burns and Dr. Ryder have
recently published the first Australian based research paper documenting bacterial activity
during flood events using a recently developed fluorometric technique.
Bruce Mullins
Bruce is the Manager of Johnstone Centre – Environmental Consulting and will act as
Project Manager. Bruce has extensive experience in planning and conducting flora and
fauna surveys as well as planning, costing and organising large-scale operations. He has
planned, managed and written numerous reports for the government and private sectors. He
has comprehensive knowledge of Federal, State and local government legalisation and
planning.
Lachlan Sutherland
Lachlan is a consultant with Johnstone Centre - Environmental Consulting. He is an
ecologist with experience in ecological assessment, riverine ecosystems and GIS. He has
recently completed an Honours degree studying the effects of cattle on microinvertebrate
diversity in selected billabongs on the Murrumbidgee River Floodplain. He also possesses
excellent data management, report writing and liaison skills and has experience in the
review of biodiversity literature.
MARTIN ASMUS
Martin is a Technical Officer and has been involved in a wide range of research projects in
aquatic systems, including research on environmental flows in the Murrumbidgee River
and review of weirs in the Murrumbidgee and Murray rivers.
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6.0 SUPPORTING INFORMATION
6.1
Johnstone Centre
The Johnstone Centre is one of five research centres at Charles Sturt University. The
Centre is made up of academics, postgraduate students, consulting staff and support staff.
The Johnstone Centre’s mission is to research the fundamental ecological processes
involved in the conservation of the diverse range of ecosystems and protected areas in
Australia and overseas, which is crucial to their successful management.
Our research contributes to developing a greater understanding of ecological processes on
a community and landscape scale and applies the results of such research to challenge
current practices, policies and planning. These studies enable us to establish the conditions
necessary for ecologically sound management, as well as biodiversity assessment and
conservation evaluation.
Johnstone Centre - Environmental Consulting and associated academics have worked
extensively in the riparian zones of the Murrumbidgee Catchment, with research focused
on biodiversity, flora and fauna surveys, environmental flows and the impacts of
agricultural practices on riparian zones.
6.2
Insurances
The Johnstone Centre is covered by insurance policies held by Charles Sturt University. A
Workers Compensation Policy is held with MMI Insurance Group (Policy No. MWR
0024606) and Public Liability and Professional Indemnity Policies are held with Uni
Mutual (Policy No. AU CSU 990002).
6.3
Management System
Quality assurance is a key part of work in a consulting environment. Charles Sturt
University has processes in that place ensure proper management and project function.
The Office of Research and Consultancy (ORC) contains records of contracts, budgets,
reports and other key documents and is independently audited. ORC has an established
policy for Outside Professional Activity by staff, which adheres to a number of steps
critical in establishing outside consultancies.
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Within the Johnstone Centre, the Environmental Consultancy Management Committee is
made up of the Centres Director, Professor Alistar Robertson, Associated Director, Dr
Allen Curtis and other senior researches. Documents are reviewed prior to release for
correct spelling and grammar, appropriate use of scientific methods and whether
conclusions, recommendations or proposed strategies are sound. A Directors Project
Review Form can be inserted into a document to certify that the document has been
reviewed to the satisfaction of the review committee and what it has been reviewed for.
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Ammendments Requested by Murray Darling Basin Commission
Brian Lawrence
Manager, Rivers Program
Murray Darling Basin Commission
Dear Brian,
Following are response to the seven questions provided in your fax.
Question 1. Could you state more explicitly the hypotheses – the questions that are being
addressed in each of the monitoring themes.
Water quality
Hypothesis.
2. The concentration of DOC, POC and suspended solids will increase during the variable
flow releases compared to constant flows as a result of increased riverbank and
floodplain inundation and in channel resuspension. We predict there will be increased
loading of carbon with distance downstream.
Water quality parameters listed in the tender will be used as covariates for the
interpretation of biofilm composition and productivity and macroinvertebrate data.
Physical habitat stability
Hypothesis.
1. Peak flow releases will lead to bed-load movement in cobble habitats and result in the
erosion of fine sediments in habitats with increased water velocity.
Biofilm composition
Based on the results of Watts et al (2001) we predict that if there are forty days of constant
flow releases after the final harmony release, the biofilms will reach a stable state for
biomass, composition and productivity. These data will be compared to the data collected
during the harmony releases.
Hypotheses.
3. Algal and total biomass from cobble substrata will decrease following peak flow
releases compared to the biomass prior to the release due to scouring from increased
velocity.
4. Peak flow releases will change the community composition of algal biofilms and
promote early successional algal taxa on cobble substrata due to scouring from
increased water velocity.
Benthic Metabolism
Hypotheses.
3. Peak flow releases will increase carbon respiration of biofilms on cobble substrata from
deep habitats due to scouring from increased water velocity and light deprivation from
increased water depth.
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4. Newly wetted cobble with established biofilm communities will have increased carbon
production relative to those newly wetted cobbles that do not have an established
biofilm community.
Enzyme activity
Hypotheses.
3. Peak flow releases will increase the overall enzyme activity of biofilms (specifically
increase the activity fatty acids and proteins) on cobble substrata due to scouring from
increased velocity.
4. Variable flow releases will increase the overall enzyme activity in the water column
(specifically increase the activity fatty acids and proteins) due to increased riverbank
and floodplain inundation and in channel resuspension. We predict there will be
increased overall enzyme activity with distance downstream.
Macroinvertebrates
The samples collected during the forty days of constant flow releases after the final
harmony release will be compared to the data collected during the harmony releases.
Hypotheses
3. Variable flow releases will increase algal diversity on cobble substrata and will result
in a higher diversity of macroinvertebrates in cobble habitats.
4. Variable flow releases will increase algal diversity on cobble substrata and increase the
relative abundance of primary consumers on cobble habitats.
Question 2. Can you include continuous turbidity measurements, as well as advise on
constraints or difficulties with continuous monitoring equipment and suggest responses?
Yes. We have three Yeo-kal multiprobes that can be used to continuously monitor
turbidity, pH, Conductivity, DO (mg/L) and Temperature. These multiprobes can be set up
at sites 1, 3 and 6 to continuously monitor parameter trends in the Mitta Mitta over the
entire assessment period. The multiprobes will be calibrated and the data downloaded
regularly during the collection of water quality samples to ensure quality of data. There are
no foreseen constraints of difficulties with the use of this equipment.
Question 3. Would Dr Watts be available for greater input into the preparation of the
report?
Dr Robyn Watts, Dr Darren Ryder and Professor Alistar Robertson are available for
greater input into the preparation of the report. Dr Watts will analyse and interpret the
macroinvertebrate and water quality data. Dr Ryder will analyse and interpret the biofilm
and water column metabolism data and the enzyme activity results. Prof Robertson will
calculate the POC and DOC loads. The time allocated to Lachlan Sutherland will be
reduced to allow for increased input of the above members.
Question 4. Would you be able to include some direct measurements of the impact on
physical habitat?
Yes. Direct measurements of the impact on physical habitat can be measured in both the
upper and lower reaches of the Mitta Mitta River. These measurements will include the
movement of cobbles in response to the variable flow releases.
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Method: Cobbles of small, medium and large diameters will be selected at each of the three
Mitta Mitta River sites, 1, 3 and 6. One third of the cobbles from each of the size classes
will be recovered following flow period 2, one third following flow period 3 and one third
forty days after the end of the harmony releases. Presence or absence of marked cobbles
will determine the impact of single flood events and combined flood events on cobble
movement.
The second measurements will be based upon removal / accrual of sediment in the lower
reaches, within the bed and on the banks at certain sites along the Mitta Mitta River.
Method: This method will be used at sites 3 and 6 (depending upon sediment type). Metal
rods will driven into the sediment across the channel of the Mitta Mitta River. These rods
will cover the river bed and banks. Metal discs (with centre punched holes) will then be
placed onto each rod. The disks will be free moving. The rod will be marked at the original
position of the disk. After each flow event the amounts of sediment accrual and/or removal
can be calculated. The technique will quantify the extent of sediment scouring (removal) or
deposition.
Question 5. Can you advise on how you will maintain awareness of river operations and
what flexibility you have in responding to changing weather and release conditions?
Dr Watts has spoken to Gary Tuenon (Dartmouth Dam) and he indicated that instantaneous
river heights at Colemans and Talladoon gauges are available via telemetry on numbers
that will be provided to us. He also indicated that information on the 24hour releases will
be faxed to us on request.
Question 6. Would you be able to include an external peer review function for your draft
report?
Yes. Dr Watts has contacted Craig Schiller from Water Ecoscience (Victoria) and Jane
Roberts, Independent Consultant, in respect to this request. Both Craig and Jane have
agreed to review the report.
Craig Schiller has been part of the Mitta Mitta River Monitoring Group responsible for
monitoring macroinvertebrates within this system since 1986. Reference was made to their
1999/2000 report in our original quote. (AWT 2000). Craig also peer reviewed Watts et al
(2001), ‘Assessment of Environmental Flows on the Murrumbidgee River’. Craig requires
has indicated that his fee will be $1000 to review this document.
Jane Roberts is an independent consultant, and was previously a Senior Research Scientist
with CSIRO. Jane is a member on the Technical Advisory Panel for the Clarence River,
has several expert panels for the assessment of river health and is currently part of the
Lower Snowy River Rehabilitation Trial Project. Jane also reviewed Watts et al (2001).
Jane requires one day to complete the review and has indicated that her fee will be $1100
inclusive of GST.
Robyn Watts
Charles Sturt University
27/11/2001
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