The Effects of Climate Change on Benthic
Macroinvertebrate Communities
Ecological Risks Associated with
Future Anthropogenic Impacts in
Vermont’s Streams
By: Tanner Williamson, Samuel Parker, Emily Matys
Jacqueline Maisonpierre & Pace Goodman
Overview
 Combined effects of climate change and urbanization are changing the
ecology of Vermont’s streams
 These changes will affect communities of benthic macroinvertebrates
(BMI)
 Goal of this project was to use benthic macroinvertebrates as an
indicator of stream health as to evaluate the impacts of climate change
and urbanization on Vermont’s streams
 We found the compounding effects of urbanization to pose the largest
potential threat to BMI populations
Approach:
EPA’s Ecological Risk Assessment framework
 Emphasized problem formulation, data analysis and risk characterization
Data Collection
Problem Formulation
Analysis
Effects Exposure
Risk Characterization
Risk Management
Location of study
 Papers were relatively rare, so best judgment was used on which data to utilize
 However, all assisted in gaining depth of knowledge concerning benthic
macroinvertebrates
 Individuals, species, and communities
The theory of stationarity
 Variables chosen for analysis were studied in past conditions
 Must assume conditions at that point in time are similar to those into the future
 Additional environmental and ecological variables may change in years to come
Background:
Climate Change Scenarios
High Emission Scenario:
 Winters could warm by 8 to 12°F and summers by 6 to 14°F by the year 2100
 More precipitation will fall as rain and less as snow
 Drought frequency in late summer and fall is projected to increase significantly
 Seasons are expected to shift, spring will be earlier and potentially wetter and fall
could become drier
Low Emission Scenario:
 Temperature increases of 5 to 7.5°F in winter and 3 to 7°F in summer by the
end of the century
Under Both Scenarios We Expect to See…
 Increased winter precipitation as rain
 Increased magnitude and frequency of heavy rain events, which, in turn, will cause
an increase to the magnitude and frequency of large flow events in stream and
river channels
Macroinvertebrate
Information:

Benthic macroinvertebrates are
small, aquatic organisms that
inhabit the substrate on the bottom
of streams and rivers.

Orders Commonly Found in VT:
(a) Ephemeroptera (Mayflies)
(b) Plecoptera (Stoneflies)
(c) Trichoptera (Caddisflies)
Diptera (True flies)
Coleoptera (True beetles)
Megaloptera
Primary Consumers
Feed on detritus or other
macroinvertebrates
Sensitivity to stressors in the
aquatic system make them
excellent biological indicatory
species
(a)
(b)
(c)
(c)

Climate Change
Higher Ambient
Temperatures
Urbanization
Extreme Precipitation
Events
Increased Impervious
Surfaces
Sources
Concept Model:
Extreme Flow Events
Stressors
Water
Temperature
Increase
Low Flows
(Droughts)
High Flows
(Floods)
Decrease in D. O.
Concentration
Effects
Increased
Siltation
Increase in
Respiration
Rate
Organism
Stress/Morality
Habitat Loss
Endpoints
Shifts in Benthic
Macroinvertebrate
Communities
Increased
Erosion
Decrease of Fecundity and
Changes in Trophic Structure
Figure. Conceptual model exploring the sources (rectangles), stressors (hexagons), effects
(parallelogram), and endpoints (ovals) of human impacts on benthic macroinvertebrates.
Variables Influencing
Stream Health Considered
 Dissolved Oxygen
 Sedimentation Loads
 High Flow Events & Drought Events
 Compounding Effects of Urbanization
Drought
Events
http://blogs.tnr.com/tnr/blogs/environmentandenergy/archive/2009/02/02/california-s-snowpack-problem.aspx
What is drought?
(Modified from: Boulton 2003)
Macroinvertebrate response to drought
(Modified from Boulton 2003)
MIV response to drought (cont.)
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
(Modified from Suren 2006)
Drought: Climate Considerations
(Modified from Hayhoe et al. 2006)
Drought: Climate Considerations (Cont.)
(Hackett 2009)
High Flow Events
Increased storm frequency and intensity as a result of Climate Change
Graph #1
Graph #2
Graph #3
Projected increases of extreme precipitation (1) Precipitation intensity
(2) Number of days per year with > 2” of rain (3) Maximum amt. of rain to fall
During a 5 day period (NECIA-Northeast Climate Impact Assessment 2006)
Effects of High Flow Events on Macroinvertebrates
• Flood events cause physical scouring and moving of the riverbed
• Macroinvertebrates can be crushed or swept into the stream flow
• Communities are resilient, Bradt et al. (1999) found stability and
resilience in BMI assemblages in a PA river over 25 years
• Life history strategies of asynchronous, multivoltine life cycles aid in
the stability of maroinvertebrate communities
High Flow Events
• Marked decrease in all groups of taxa post
flooding events
• Resilience shown in all species
• Capacity to return to some previous state
following a perturbation
• In Suren & Jowett (2001) study relative
abundance of 14 taxa increased after small
floods while abundance of 10 taxa decreased
after the largest flood
Figure. Relative flow of the Waipara River and relative
density of selected invertebrate taxa averaged across
riffles and runs collected in the Waipara River between
September 1998 and June 2001 (Suren and Jowett 2007)
Sedimentation
 Climate change has the potential to indirectly increase the rates of
erosion and sedimentation
 Increased storm events
 Presently, 34% of United States waters deemed impaired are due to
excessive sedimentation
 Climate change along with anthropogenic stressors (i.e. urbanization)
have great potential to influence macroinvertebrate populations
Effects of Sedimentation on Macroinvertebrates
 Most populate stream segments composed of cobble and pebble substrates
 Size of particles is incredibly important in survivorship
 Suspended and deposited sediments modify the habitat structure
 Limit interstitial space
 Inhibits filter feeders
Increased fine sediment
 Kaller et al. 2004 found fine particles (<0.125mm) are detrimental to
EPT taxa along with overall macroinvertebrate density, biomass and
taxa richness
 Identified a threshold for BMIs at a percent of fine sediments >0.8%
 Decline in richness at a percent of fine sediments >0.8%
 Richness was preserved where fine sediment did not reach 0.8%
Sensitivity of Macroinvertebrates
 Some sensitive species cannot adapt to increases in fine sedimentation
 Those who rely on substrates for attachment
 Threshold of fine sediment is increased for scrapers and grazers to 40%
 Burrowing species have the potential to benefit from an increase in fine
particulates
 Changes in individual abundance will be most effected rather than
diversity
Contradictory studies
 Vasconcelos et al. 2008 found that coarse sediment (0.25-0.80mm)
was most detrimental to macroinvertebrates
 Abrasion was the cause of most mortality
 Larsen et al. 2009 found no correlation between increased sediment
and macroinvertebrate species
 Results proven to be related more closely to land use and water
quality
Dissolved Oxygen
Dissolved Oxygen
(Ficke et al. 2007)
Increased Air
Temperature
Higher Metabolic
Rates
Increased Water
Temperature
Reduced DO
Dissolved Oxygen
(Jacobsen et al. 2008)
 Eight Unpolluted Sites:
 No correlation between DO fluctuations (max, mean and min) with
BMI indices
 All Twelve Sites:
 Positive correlation between BMI indices and O2 saturation
 Minimum DO had more significance than mean DO
Dissolved Oxygen
(Beyenne et al. 2007)
 Diatoms serve as better stream health indicators due to reduced
vulnerability
Variable Interactions
Reduced DO
Higher Flow Events
More Drought
More Sedimentation
Compounding Effects of Urbanization
The relationship between TIA and EPT
richness for urban and rural reaches
(Modified from: Fitzgerald 2007).

The direct link between stream health and
urbanization makes it difficult to precisely
identify the stressors associated with climate
change.

Urbanization ultimately increases the
impervious cover of a watershed.
 High flow events would be more likely,
which could increase erosion and
sedimentation.
 The water running off the impervious
surfaces is likely to be much hotter than
water running off a shaded forest, which
would increase water temp and decrease
DO.
 A loss in vegetation could reduce the ET
flux and make droughts more likely.
Risk
Assessment
Relative risks to stream BMI communities at
three different intensities of urbanization
Percent Total
Risk
Source
Impervious Area
Rank
5.0% 10.0% 25.0%
Low Flows and
1
5
10
25
Droughts
High Flow Events
2
10
20
50
Sedimentation
3
15
30
75
Dissolved Oxygen
4
20
40
100
Net Effect
10
50
100
250
First, We assigned a risk rank.
1.
Low Flows and Droughts
2.
Increased Flow Events
3.
Sedimentation
4.
Dissolved Oxygen
Then, simply multiplying by the relative
risk rate by the total impervious area
we can get a scaled net effect of
Climate Change and Urbanization on
Macroinvertebrate Communities
Expanding
Effect
1.
Game Fish
2.
Water Quality
3.
Any other ideas?
4.
Any other ideas?
Recommendations
• Halt or mitigate future anthropogenic climate
change by:
• Reducing Greenhouse Gas emissions
• Reduce draw-downs during low flow periods
• Promote the development of mature riparian forests
to:
• Provide shading
• CWD habitat
• Air & surface water temperature
moderation
• Reduce sedimentation
• Improve water quality
• Develop land use practices that:
• Reduce the % of impervious surfaces
• Encourage less intensive agricultural tillage
techniques
Hybrid Vehicle
Rain Garden
Recommendations (Cont.)
Healthy Riparian Buffer
Poor Riparian Buffer
Questions…
Oh No,
Climate
Change!!