Aquatic Plant Survey of Serene Lakes
For
Sierra Lakes County Water District
PO Box 1039
Soda Springs, CA
530-426-7800
By Catherine Schnurrenberger
Botanist
C.S. Ecological Surveys and Assessments
Truckee, CA
530-448-6847
October, 2013
Definitions of Biological Terms
Akinetes - dormant cells of cyanobacteria specifically Gloeotrichia sps.
Benthic – (Of the benthic zone) The benthic zone is the ecological region at the lowest level of a body of
water such as an ocean or a lake, including the sediment surface and some sub-surface layers.
Cyanobacteria - (blue-green algae) are prokaryotic, bacteria-like organisms that thrive in extreme
habitats and those that are nutrient enriched.
Eutrophic Lake - A eutrophic body of water, commonly a lake or pond, has high biological productivity.
Due to excessive nutrients, especially nitrogen and phosphorus, these water bodies are able to support
an abundance of aquatic plants. Usually the water body will be dominated either by aquatic plants or
algae. When aquatic plants dominate the water tends to be clear. When algae dominate the water tends
to be darker. The algae engage in photosynthesis which supplies oxygen to the fish and biota which
inhabit these waters. Occasionally an excessive algae bloom will occur and can ultimately result in fish
kills due to respiration by algae and bottom living bacteria. The process of eutrophication can occur
naturally and by human impact on the environment.
Hypolimnion - the deepest water level
Limnology - The scientific study of the life and phenomena of fresh water, especially lakes and ponds
Macrophytes - A macrophyte is an aquatic plant that grows in or near water and is either emergent,
submergent, or floating. In lakes macrophytes provide cover for fish and substrate for aquatic
invertebrates, produce oxygen, and act as food for some fish and wildlife.
Mesotrophic Lake - lakes with an intermediate level of productivity and nutrients. These lakes are
commonly clear water lakes and ponds with beds of submerged aquatic plants and medium levels of
nutrients.
Oligotrophic Lake - An oligotrophic lake is a lake with low primary productivity, the result of low
nutrient content. These lakes have low algal production, and consequently, often have very clear waters,
with high drinking-water quality. The bottom waters of such lakes typically have ample oxygen; thus,
such lakes often support many fish species, like lake trout, which require cold, well-oxygenated waters.
The oxygen content is likely to be higher in deep lakes, owing to their larger hypolimnetic volume.
Phytoplankton - small often microscopic vegetation that are free floating in water.
Plankton - small often microscopic organisms that are free floating in fresh or salt water.
Rhizomes - Lateral roots that often form at nodes in aquatic plants such as Potamogetons.
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Introduction and Purpose
Catherine Schnurrenberger, Botanist at C.S. Ecological Surveys and Assessments (CSESA), was contracted
by Bill Quesnel, the Operations Manager for the Sierra Lakes County Water District, to conduct an
aquatic plant survey to provide baseline data to support preparation of a comprehensive Lake
Management Plan for the Serene Lakes. Lake Serena and Lake Dulzura collectively referred to as “Serene
Lakes” are both currently used for recreation and Lake Serena is use as a drinking water supply for the
Serene Lakes community.
Serene Lakes were originally three separate lakes, Serena, Dulzura and Sybil until 1941 when the lower
lake, Dulzura, was damned (Attachment A). The smaller Sybil Lake was incorporated into Lake Serena
and there is no separation between these, though Lake Serena and Lake Dulzura are connected by
surface water they are still referred to as separate lakes. The Sierra Lakes County Water District was
established in 1966 to provide the drinking water supply for the home owners at Serene Lakes. In the
1980’s in response to complaints about the extent of macrophytes, (aquatic vegetation visible without
magnification), Lake Serena was partially drained and dredged. It is likely that this only resulted in a
temporary reduction in vegetation growth. Water quality parameters such as nutrient levels,
temperature and dissolved oxygen have been periodically sampled in both lakes, but no long term plan
for assessing water quality has been in effect. In 1991 a more comprehensive study assessing the
limnological conditions in Serene Lakes was conducted by Gary Vinyard with the University of Nevada,
Reno. No non-native invasive aquatic plants were noted to be present in the lakes during this study nor
have such plants been reported in any subsequent studies or surveys.
Description of Study Area
Lake Serena and Lake Dulzura are both described as “moderately productive mesotrophic lakes”,
meaning that they have moderate levels of dissolved nutrients. The level of dissolved nutrients is limited
by the seasonal stratification of the lakes during the summer and winter which reduces or eliminates the
exchange of nutrients between bottom sediments and the water column during that time. Aquatic
macrophytes, cyanobacteria (blue-green algae), and phytoplankton (photosynthesizing microscopic
organisms present in the upper layers of most water bodies) require both sunlight for photosynthesis
and nutrients for metabolic processes therefore when nutrients are isolated from surface waters due to
stratification they are not available to these photosynthesizing organisms, which limits the growth of
these organisms.
Methods
On October 1st, 2013 Bill Quesnel and Catherine Schnurrenberger used a small boat to visit shallow areas
throughout Serene Lakes that might be suitable for aquatic macrophytes. All equipment used for
collection had not been used in other water bodies thus eliminating the potential for introduction of
invasive aquatic organisms. A Garmin CSX global positioning unit (GPS) was used to record both the
tracks of the survey and any points of interest recorded during the survey (Attachment B). All observed
aquatic vascular plants and two species of algae were collected for identification and areas with high
concentrations of aquatic plants and/or algae were noted.
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Findings
Six species of aquatic vascular plants, one multicellular algae and two blue-green algae or cyanobacteria
were identified during the surveys (Attachment C). No non-native invasive aquatic vascular plants were
observed at Serene Lakes. All vascular plants observed were rooted to the lake bottom and were in
depths of less than 3 meters. All but two pondweed species were limited to areas less than 2 meters
deep. The multicellular algae, stonewort (Nitella sp.), was observed at depths of up to 3 meters
however it may occur deeper depending on water clarity. The cyanobacteria Rivularia sp. appears to be
attached to all aquatic vegetation and is also most likely attached to bottom sediments and substrates.
A free floating planktonic cyanobacteria Gloeotrichia echinulata also appears to be present in Serene
Lakes.
Vascular Plants
Sturdy Bulrush (Bolboschoenus robustus) is a perennial wetland graminoid in the sedge family. This plant
forms dense colonies connected underground by stout lateral roots or rhizomes. No flowering heads
were present therefore the identification to the species level was not definite but the length, abundance
and pattern of the leaves suggest that the Bulrush observed during the survey was Sturdy Bulrush.
Sturdy Bulrush was found in water less than 2 meters deep in both Lake Serena and Lake Dulzura. There
were several large populations of Sturdy Bulrush on the southwest shore of Lake Serena (Attachment B
and D) and one near the outflow of Lake Dulzura. Only the population on the southwest shore of Lake
Serena appears to be in good health, all other plants of Sturdy Bulrush are infested with cyanobacteria.
A list of all species observed is presented in Attachment C and photos of each genus are presented in
Attachment D.
Buckbean (Menyanthes trifoliata) is a perennial aquatic plant in the Buckbean family with thick
rhizomatous roots which spread laterally across the water surface (Attachment C and D). This species
was found only along the edges of Serene Lakes at depths of up to 1 meter. It appears to root at the
margin of the lake where the rhizomes or lateral roots spread out into the open water. This species can
form dense colonies and it is reported that it may grow from broken fragments of roots and branches.
The most common, widespread, aquatic vascular plant found was Broad Leafed Pondweed
(Potamogeton amplifolius) a perennial aquatic plant in the pondweed family. This species was found at
depths up to 3 meters in both lakes (Attachment B). Broad Leafed Pondweed is a perennial with stout
rhizomes that allow for extensive vegetative reproduction. This species often forms large mats or
colonies (Attachment D). The largest population of Broad Leafed Pondweed is along the edge of a sharp
drop off in the middle of Lake Dulzura and is approximately 70 meters by 17 meters (Attachment B).
Nuttall’s Ribbon-leaved Pondweed (Potamogeton epihydrus ssp. nuttallii) is a perennial Pondweed with
slender rhizomes that can form dense mats. Nuttall’s Ribbon-leaved Pondweed is ranked as a rare plant
in California by the California Native Plant Society (CNPS 2013). It has a rare plant ranking (CRPR) of 2.2,
which means that it is rare in California and its survival is moderately threatened by recreational
activities and water contamination. Currently there are no legal requirements for conservation of rare
plants with a ranking of 2 or higher and no State or Federal status. This species was previously observed
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in Lake Dulzura by North Fork Associates (NFA 2008) as part of an inventory for the Royal Gorge
development project. During this survey Nuttall’s Ribbon-leaved Pondweed was found near the outflow
of Lake Dulzura and in a cove to the northwest of Lake Dulzura. It is likely that it is more widespread
within Lake Dulzura and it could be present in Lake Serena.
Leafy Pondweed (Potamogeton foliosus var. foliosus) is an annual or weak perennial species which rarely
produces rhizomes that is widespread throughout both lakes but in low numbers. Its leaves were most
often observed floating in the water column after it had detached from its root system.
White-stemmed Pondweed (Potamogeton praelongus) is a perennial pondweed with stout rhizomes.
This species has a rare plant ranking of 2.3 indicating that it is rare in California but not threatened
(CNPS 2013). White-stemmed pondweed species are known to hybridize with broad-leafed pondweed
and it is possible that the plants observed in Lake Dulzura are indeed hybrids. Due to the late sampling
time and the poor condition of the plants that were infested with the cyanobacteria, a positive
identification was not possible however the clasping leaves indicate that the plants are either Whitestemmed Pondweed or a hybrid. This species was only observed in one location in a cove on the
northwest edge of Lake Dulzura (Attachment B). More extensive surveys during the flowering period in
August may reveal more populations of this species at Serene Lakes.
Multicellular algae
Stonewort (Nitella sp.) is a multicellular algae in the Characeae family that roots in lake sediments.
Stonewort is similar in appearance to a flowering plant but it does not produce flowers, instead female
reproductive organs called oogonium and male reproductive organs called antheridium are produced in
the axils of whorled branches (UMASS 2013). Stonewort species can establish at depths over 3 meters in
clear water. This species was observed throughout both lakes but never in large populations.
Cyanobacteria
Cyanobacteria or blue-green algae are prokaryotic, bacteria-like organisms that thrive in extreme
habitats and those that are nutrient enriched. Cyanobacteria was found on aquatic plants within Serene
Lakes. It was prevalent on all species of aquatic plants often covering more than 70% of the surface area
(Attachment C). This cyanobacteria, which is either Rivualria or Gloeotrichia both within the
Rivulariaceae family, appears to be harming the plants which were in poor condition. Because all but
one account of Gloeotrichia by Prescott (1978) refer to this species as being planktonic, or free floating
on the water surface, and the cyanobacteria were mostly observed attached to aquatic vegetation there
may be two species of cyanobacteria in the lakes, Rivularia on plants and Gloeotrichia within the water
column. The most prevalent species is the one attached to aquatic plants. This cyanobacteria forms
gelatinous hemispheric sacs with many filaments radiating out from a central point towards the edges of
the sac. Each filament is made up of multiple cells of the cyanobacteria either Rivularia or Gloeotrichia.
The floating cyanobacteria are Gloeotrichia most likely Gloeotrichia echinulata also in the Rivulariaceae
family. Gloeotrichia has been reported mostly from the planktonic community meaning that it is free
floating on the water surface and within the water column. This was observed on October 5 th when I
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went to collect water samples to observe if any cyanobacteria were suspended in the lake water.
Research on this species has shown that Gloeotrichia is often concentrated in shallow downwind areas
where predominant winds blow the free floating colonies (see Attachment E for more information on
Gloeotrichia echinulata). Because Gloeotrichia is normally active in August and begins to sink to the
bottom of the lake and settle on lake sediments during its dormant period in winter I stirred up
sediments before collecting water samples. Gloeotrichia has been reported in lakes within the Tahoe
region (per. communications D. Hunter). This species was associated with eutrophic lakes with high
nutrient inputs however within the past 30 years this species has been reported in mesotrophic and
oligotrophic lakes in the northeast of the United States (Carey et al. 2012).
Recommendations
One concern of home owners in the Serene Lakes area is the nuisance of large populations of aquatic
vascular plants. Buckbean often covers shoreline areas requiring people to wade through this plant to
launch kayaks and other water craft. Sturdy Bulrush and pondweed are present in both Lake Serena and
Lake Dulzura near swimming and boating areas. None of these aquatic vascular species are invasive
weeds, nor are they present in unnatural numbers. It would not be prudent to try to extract these plants
by dredging because they would most likely re-sprout from their extensive network of rhizomes and/or
establish from plant fragments. Buckbean could be trimmed back during the summer season thereby
creating paths to the shore; more extensive removal of aquatic plants would not be ecologically
responsible nor would it be effective in the long term.
A much greater concern for the water quality and health of Serene Lakes is a potential algal bloom that
could be produced by the cyanobacteria present within the lakes. The brief survey conducted in October
indicates that there is an infestation of the Rivularia or Gloeotrichia on the aquatic vegetation. The level
of Gloeotrichia in the water samples was very low, however this cyanobacteria blooms in August and
therefore water samples for this species should be collected during that time.
It is important to assess not only the levels of the cyanobacteria identified in this report but also to
identify which other species of algae and cyanobacteria are present within Serene Lakes and at what
concentrations. Another very common cyanobacteria in the local area is Nostoc, which settles on
substrates and plants and blooms in response to high levels of dissolved nutrients. Other species of
algae and cyanobacteria are most certainly present in Serene Lakes but this study did not focus on
sampling of the phytoplankton. There is evidence that cyanobacteria within the Rivulariaceae family
may increase growth of other phytoplankton thus identifying the other species of algae and
cyanobacteria present within the planktonic and benthic community will help inform the water district
about potential algal blooms (Carey and Regefors 2010). The planktonic cyanobacteria Gloeotrichia can
translocate phosphorous from lake sediments to the water column increasing the availability of this
nutrient to other algae potentially leading to algal blooms of other species. Because many cyanobacteria
are nitrogen fixers, phosphorous is usually the limiting nutrient to growth. Blooms of certain algal
species can have direct and indirect deleterious effects on the aquatic community. Algal blooms not
only create visual pollution in the lake they can also decrease dissolved oxygen which can lead to fish
kills. In addition both species of cyanobacteria produce microcyistin-LR which can be toxic to
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macrophytes, can potentially cause skin irritation in humans, and at high levels, if ingested, can affect
processes in the liver of humans and animals.
Sampling of the planktonic and benthic communities should be conducted where and when known or
suspected algae and cyanobacteria are at their highest concentrations. This may involve multiple
sampling times during the season and multiple sampling locations throughout the lakes. Research on the
viability of Gloeotrichia akinetes or dormant cells found that even when similar numbers akinetes are
present on sediments those at shallow depths are much more likely to produce active cells in the spring,
the same study found temperature and light the most important factors in initiating germination of
Gloeotrichia cells (Karlsson-Elfgren et al. 2004). This indicates that sampling Gloeotricha colonies at
shallower depths may be of higher priority. Other species of algae and cyanobacteria will have different
habitat preferences.
As well as measuring the current and future levels of algae and cyanobacteria it is important to assess
water quality parameters that may influence the growth of these organisms. These parameters should
include but not necessarily be limited to:
1) the level of phosphorous in the water column and in lake sediment,
2) levels of light and depth of light (measured with a secchi disk), and
3) water temperature at different depths
Knowing the current levels of these parameters may indicate which parameter(s) is/are likely to drive
the growth of Gloeotrichia, Rivularia or other algae and/or cyanobacteria. Even if it is not possible to
isolate the factors controlling the current growth of these organisms, by tracking the levels of these
parameters over time the Sierra Lakes County Water District may be able to detect a trend which will
indicate if algal blooms are likely to occur and if such blooms may affect the health of the lake
environment and/or the toxicity of drinking water taken from Lake Serena.
Past data indicates that light at the bottom of Lake Dulzura is sufficient to support growth of algae. In
the 1991 Limnological Report, Vinyard states that “Chlorophyll concentrations were high in the
hypolimnion of Lake Dulzura.” The hypolimnion is the deepest water level and it has the lowest level of
dissolved oxygen. Vinyard also states that “the relatively large secchi depth suggests that photosynthesis
is possible at the depth of the hypolimnion, providing a low light intensity refuge for algae…” (Vinyard
1991). These conditions would provide favorable conditions for Gloeotrichia when it commences growth
in the spring.
Water temperature data should be examined to detect if there has been a trend towards warmer water
temperature. The previous two water years have been well below average leading to lower water levels
in local lakes making the overall water temperature warmer and allowing more light to penetrate to
bottom sediments. It would be valuable to quantify the change of temperature in of both Lake Serena
and Lake Dulzura. There may be a correlation between these temperature increases and the increased
C.S. Ecological Surveys and Assessments
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growth of Rivularia and/or Gloeotrichia as such temperature increases may lead to blooms of
Gloeotrichia.
Identifying inputs of sediment and phosphorous will be useful in reducing the level of phosphorous in
lake sediments in the future. Possible sources include but are not limited to: detergents and soaps used
in washing boats or vehicles, road sand used in winter, natural sediments from upslope erosion, pet and
human waste and fertilizers. Continuing education of homeowners and users of Serene Lakes regarding
the impacts of phosphorous will be helpful in controlling inputs to the lakes of this nutrient.
The future climatic conditions for the Sierra Nevada area are uncertain. Predictions for the region
include warmer winters, an increase in rain versus snow, larger storm events and overall warmer
temperatures. All of these changes would favor eutrophic lake conditions what would support not only
the growth of Gloeotrichia but the growth and spread of other algae, cyanobacteria and aquatic
organisms. Monitoring the parameters that affect these aquatic organisms will help the Serene Lakes
County Water District to prepare for future changes and address potential threats to water quality and
recreational activities.
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References
California Native Plant Society (CNPS). 2013. Inventory of Rare and Endangered Plants (online edition,
v8-02). California Native Plant Society. Sacramento, CA. http://www.rareplants.cnps.org. Accessed
Friday, October 04, 2013.
Carey, C.C., H.A. Ewing, K.L. Cottingham, K.C. Weathers, R.Q. Thomas and J.F. Harvey. 2012. Occurrence
and toxicity of the cyanobacteria Gloeotrichia echinulata in oligotrophic lakes in the northeast of the
United States. Aquatic Ecology, Vol. 46 Issue 4 pp. 395 – 409.
Carey, C.G. and K. Regefors. 2010. The cyanobacterium Gloeotrichia echinulata stimulates the growth
of other phytoplankton. Downloaded from http://plankt.oxfordjournals.org/ by guest on October 9,
2013.
Carey C.C., Weathers K.C., Cottingham K.L. (2009) Increases in phosphorus at the sediment-water
interface may accelerate the initiation of cyanobacterial blooms in an oligotrophic lake. Verh Int
Verein Limnol 30:1185–1188
Karlsson-Elfgren, I.; Rengefors, K.; Gustafsson, S. 2004. Factors regulating recruitment from the
sediment to the water column in the bloom-forming cyanobacterium Gloeotrichia echinulata.
Freshwater Biology: Vol. 49 Issue 3. Pp. 265 – 273.
LSPA (Lake Sunapee Protective Association). 2013. Gloeotrichia echinulata: an alga blooming in Lake
Sunapee. Lake Sunapee Protective Association Web page. Accessed at:
http://www.lakesunapee.org/record_images/pdf/39.pdf
NFA (Northfork Associates). 2008. Biological Resources Assessment for the +/- 2,922 acre Royal Gorge
Property, Placer and Nevada Counties CA. Feb. 2008. Unpublished
Prescott, Prescott, G.W. 1978. How to know the freshwater algae. Third edition. W.C. Brown Company
Publishers, Dubuque, Iowa. 293 pp.
UMASS (University of Massachusetts). 2013. University of Massachusetts Educational website.
Accessed at: http://www.bio.umass.edu/biology/conn.river/nitella.html
Vinyard, G. 1991. Limnological Conditions in Serene Lakes: Report to Sierra Lakes county Water District
and Psomas Associates. Unpulished May, 1991.
WHO (2003) Cyanobacterial toxins: Microcystin-LR in drinking-water. Background document for
preparation of WHO Guidelines for drinking-water quality. Geneva, World Health Organization
WHO/SDE/WSH/03.04/57).
C.S. Ecological Surveys and Assessments
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Attachment A: Bathymetric Map Serene Lakes Present Day
Attachment B: GPS tracks and waypoints October 1st 2013. Map oriented to North.
Waypoint
698
699
700
701
702
703
UTMs (NAD83)
10 S 725427
4353259
10 S 725322
4353224
10 S 725252
4353720
10 S 725477
4353062
10 S 725635
4352791
10 S 725633
4352987
Elevation
Description
6888 ft
Potamogeton foliosus
6917 ft
edge of 40 foot diameter Bolboschoenus robustus patch
6904 ft
shore north side Potamogeton foliosus, P. amplifolius, Fontinales, Menyanthes trifoliata
6907 ft
6894 ft
P. foliosus, P. praelongus and P. epihydrus var. nuttallii
P. amplifolius at outflow a lot of Bolboschoenus robustus too and some P. epihydrus ssp.
nuttallii
6902 ft
200 ft by 50 ft patch of Potamogeton amplifolius
Photo
P1 10-1-2013
P 2,3, and 4 10-1-2013
Serene Lakes Aqutic Plant Report
Attachment C
List of Observed Plant Species
Lifeform
Cyanobacteria
Dicot
Diocot
Diocot
Diocot
Diocot
Monocot
Multicellular algae
Family
Rivulariaceae
Menyantheaceae
Potamogetonaceae
Potamogetonaceae
Potamogetonaceae
Potamogetonaceae
Cyperaceae
Characeae
Scientific name
Gloeotrichia echinulata
Menyanthes trilobata
Potamogeton amplifolius
Potamogeton epihydrus ssp. nuttallii
Potamogeton foliosus ssp. foliosus
Potamogeton praelongus
Bolboschoenus robustus
Nitella sp.
California Rare Plant Rank (CRPR) designations:
1B Plants rare, threatened or endangered in California and elsewhere.
2 Plants rare, threatened or endangered in California, but more common elsewhere.
3 Plants for which more information is needed – a review list.
4 Plants of limited distribution – a watch list.
California Rare Plant Rank threat categories:
.1 Seriously endangered in California.
.2 Fairly endangered in California.
.3 Not very endangered in California.
Common name
none
buckbean
broad-leaved pondweed
Nuttall's ribbon-leaved pondweed
leafy pondweed
white-stemmed pondweed
sturdy bulrush
stonewort
Notes
attached to aquatic vascular plants and sediments both lakes
along shores sheltered areas < 1m deep both lakes
common throughout both lakes at depths < 3 meters
Noted at two locations in Dulzura Lake at depths < 2 meters
occassional in areas < 3 meters deep both lakes
one location northwest cove in Dulzura lake, < 1m deep
sheltered areas < 2m deep both lakes
scattered throughout both lakes at depths of 3 meters or more
Rarity
CRPR 2.2
CRPR 2.3
Photo 1. Patch of sturdy bulrush southwest cove of
Serena Lake.
Photo 2. Large 70m by 17m area of broad-leaved
pondweed Dulzura Lake.
Photo 3. Nitella sp. or stonewort multicellular algae.
Photo 4. White-stemmed pondweed. Photo from
Calphotos online database.
Photo 5. Buckbean on shore, Serena Lake.
Photo 6. Nuttall’s ribbon-leaved pondweed. Note two
forms of leaves, floating broad and submerged at right
ribbon like.
Photo 7. Colonies of Gloeotrichia echinulata or
Rivularia on broad-leaved pondweed from Serene
Lakes.
Photo 8. Colony of Gloeotrichia echinulata magnified
approximately 50x. Diameter of each colony is about
1mm.
Attachment E: Aquatic Plant Survey of Serene Lakes
By C. Schnurrenberger
The cyanobacteria, Gloeotrichia echinulata, is a bluegreen algae in the rivulariaceae family which
overwinters on lake sediments and vegetation and moves into the water column as waters warm up in
the spring and summer (Carrey et al. 2012). This species was observed as 0.5 to 1mm wide gel filled sacs
each containing a colony with two hemispheres of filaments radiating towards the sac membrane which
was attached to aquatic vascular plants (Attachment D). Gloeotrichia appeared to infest the aquatic
vegetation in both Dulzura and Serena Lakes and may have been responsible for the poor condition of
many of the aquatic plants. This species has not been reported in the Truckee-Tahoe area and I have
never seen this cyanobacteria in local water bodies. The observed gel filled sacs each hold a colony of
Gloeotrichia and they were most likely floating on top of the water during the summer months and were
blown to shallower windward shores in the fall. The sacs are current living algal colonies, in the fall these
“parent colonies” can each produce 500 akinetes (dormant cells) that will sink to the bottom of the lakes
when the parent colony dies and remain there until spring when light and temperatures are favorable
for germination.
Gloeotrichia is found in all over the northern tier of the US and Canada, as well as on other continents.
Though no blooms Gloeotrichia have been reported in the Sierra Nevada Deborah Hunter, a researcher
at U.C. Davis has found small numbers of in Cascade Lake, fallen Leaf Lake and Upper and Lower Echo
Lakes but not within the past five years (Hunter 2013 personal communications). This cyanobacteria is
nitrogen fixing and is therefore phosphorous limited. The reason for the increased in the occurrence of
Gloeotrichia in oligotrophic and mesotrophic lakes since 2005 is not known, it is hypothesized that it
could be due to increased water temperatures and/or increased levels of phosphorous in sediments.
These lakes may still have water column nutrient concentrations that meet the established criteria for
oligotrophic lakes (mean summer epilimnion total P concentrations < 10 micrograms/Liter for
oligotrophic and 10 micrograms to 30 micrograms/Liter for mesotrophic lakes) which suggests that
elevated levels of phosphorous in the water column are not essential for algal blooms of Gloeotrichia.
Several physiological characteristics of Gloeotrichia are potentially problematic in terms of water quality.
Firstly the akinetes (dormant cells) of this cyanobacteria overwinter by attaching to sediments and
sinking to the bottom of the lake. In response to the increased light and temperature in the spring these
dormant cells germinate and grow. As they grow they take phosphorous from pore water. As colonies
become active in the spring they recruit into the water column via gas vesicles translocating stored
phosphorous with them. In eutrophic lakes Gloeotrichia overwintering in sediments and then released
into the water column can contribute up to 2/3 rds of the summer internal load of phosphorous. As a
secondary effect the phosphorous and nitrogen provided by Gloeotrichia can become available to other
algae and cyanobacteria.
Gloeotrichia also produces a low concentration of the toxin microcystin-LR which can have an adverse
effect on phytoplankton, macrophytes, zooplankton and fish. Microcystin-LR can also cause skin
irritation to swimmers and can be toxic to the human liver although it is unknown what concentration of
1
Gloeotrichia would lead to a high enough level of microcystin-LR for toxicity to be a problem. It appears
that it is difficult to treat water contaminated with microcystin-LR as microcystins are noted to be
extremely stable in water and can withstand chemical breakdown by hydrolysis and oxidation. In typical
conditions the half –life of microcystins is 10 weeks (WHO 2003). Studies have shown that a density of
250 Gloeotrichia colonies per liter of water is needed to produce levels of microsystin-LR that could have
a negative effect on macrophytes (Carrey et al. 2012). In order to produce > than 1 microgram/liter of
microcystin-LR, the level of microcystin-LR the World Health Organization considers potentially toxicity
for drinking water, a density of around 5,000 colonies/liter of Gloeotrichia would be needed (Carrey et
al. 2012). Such concentrations have only been observed in eutrophic lakes. It is important to note that
samples of Gloeotrichia have been taken from the larger water body and not from areas where
Gloeotrichia may be concentrated such as downwind areas where wind movement concentrates floating
colonies, thus there may be localized effects to macrophytes and the aquatic community from higher
concentrations of Gloeotrichia in such areas.
2