2015 baseline algae monitoring...
TRANSCRIPT
March 21, 2016
2015
Baseline Algae
Monitoring Report
230 Main Street
Bridgton, ME 04009
207-647-8580
Lakes Environmental
Association
Amanda Pratt
Colin Holme
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Summary
Recognizing the importance of understanding algae population dynamics in lakes, LEA
began monitoring epilimnetic algae in 2015. We hoped to take monthly samples from June to
September, however equipment took longer than expected to acquire, meaning that samples
were not able to be collected until July. The first year was in many ways a trial run, but never-
theless did result in some good data.
Algae samples were collected from surface waters on ten different lakes, filtered, then
counted under magnification. The genus of each algae and the number of cells present were
recorded. Multiple samples were taken from a number of lakes, allowing for comparison of al-
gae populations over time. Studying these seasonal changes in the makeup of algae populations
is important to understanding lake ecology.
This study focused on planktonic algae, which are those that are free-floating in the wa-ter, rather than attached to rocks or other material.
Summaries of individual lakes’ results are available in LEA’s 2015 Water Testing Report or on the online lake information pages, both available on our website, www.mainelakes.org.
Collecting a core sample from
the upper portion of a lake
using a Tygon® core tube.
The water collected will be
filtered and counted for algae.
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Introduction and Background
Algae are a key metric in the assessment of water quality. They are the foundation of
lake food webs, meaning that they are the food source that directly or indirectly supports much
of the animal life existing in a lake. Of course, algae are also the source of algal blooms, which
result from an over-abundance of nutrients or a lack of algae-eating organisms. Either way, al-
gal blooms are often a sign of a water quality problem, a situation that is bad for people and for
the lakes themselves.
The goal of LEA’s algae testing program is to identify the various kinds of algae present
in the lakes of the Lakes Region of western Maine, quantify them, and study how they change
over time. Algae populations change in a predictable way over the course of a year, and under-
standing which algae are present at certain times can tell us about lake conditions. For exam-
ple, diatoms are common in the early spring because they prefer colder water and well mixed
lake conditions. Large diatoms tend to settle out in the summer when waters are calmer.
There are 6 main groups of algae found in our lakes: green algae, cyanobacteria, dino-
flagellates, cryptomonads, golden algae, and diatoms. Green algae are a very diverse group;
their common characteristic is their dominant pigments, chlorophyll-a and chlorophyll-b,
which give them a deep green color. Cyanobacteria are the most liable to form blooms and are
also known for producing toxins. They are more closely related to bacteria than to other algae,
and are also known as blue-green algae. Dinoflagellates are a group made up of large, motile
algae. This group includes only a few species. Cryptomonads are one-celled algae with two
flagella which allow them to move through water. None were identified during sampling alt-
hough they are likely present in the lakes studied. The Golden algae category contains relative-
ly few species, though they are often common in low nutrient lakes such as the ones in this
study. Golden algae are a group distinguished by their brown or yellow color. Finally, diatoms
are readily identified by their hard, silica-based outer shells which make them unique from oth-
er types of algae. They are most common in the spring and fall when lakes mix.
LEA is particularly interested in learning more about the relative quantity of cyanobacte-
ria in each lake, and how this number changes over time. This is because cyanobacteria con-
centrations can tell us the most about the water quality status of a lake. High levels of cyano-
bacteria are often correlated with high phosphorus levels, and cyanobacteria such as Aphani-
zomenon, Anabaena, and Microcystis are the most common cause of algal blooms. Cyanobac-
teria tend to be most common in the later part of the summer, when temperatures are warmest.
While cyanobacteria do exist naturally in all lakes and their presence is generally not a prob-
lem, changes in the amount of cyanobacteria over the course of a year can be a water quality
indicator.
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Methods
Algae samples were collected from ten lakes one or more times between July 17th and
September 15, 2015 (Table 1). The samples were taken from epilimnetic core samples, mean-
ing they contained a composite of water from the top layer (ranging from 3-10 meters deep) of
the water column. The depth of the core was determined by temperature and dissolved oxygen
profiles. A total of 36 samples were collected.
Samples were not preserved, but stored in the refrigerator for a maximum of three days
before analysis. Samples were filtered through sand and a concentrated 1-mL subsample was
mounted on a gridded Sedgwick-Rafter slide. Ten squares on the grid were counted at 200x
magnification. The number of algal cells and the genus (the taxonomic rank above species lev-
el, plural genera) of algae they belonged to were recorded. Finally, the number of cells per mil-
liliter (cells/mL) was calculated for each sample.
Lake Name Number of Samples
Hancock Pond 4
Highland Lake 1
Keoka Lake 4
Long Lake 1 from each basin for a total
of 3
McWain Pond 4
Moose Pond 4 from the Main Basin and
4 from the South Basin
Peabody Pond 2
Sand Pond 4
Trickey Pond 2
Woods Pond 4
Table 1. Lakes sampled for algae and the number
of samples collected from each.
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Results
A total of 49 different algae genera were identified across the 10 lakes sampled. Of
these, there were 21 green algae genera, 16 cyanobacteria (blue-green algae), 9 diatoms, 5
golden algae, and 2 dinoflagellates. The average sample contained 22 unique genera. Overall,
Green algae were most common type of algae seen in the samples, followed by cyanobacteria,
diatoms, golden algae, dinoflagellates, and cryptomonads. Among the most common genera
identified were Westella (green algae), Tabellaria (diatom), Dinobryon (golden/yellow algae),
Asterionella (diatom) and Merismopedia (cyanobacteria) (Table 2).
The ponds with the highest average percentage of cyanobacteria were Woods Pond and
Moose Pond (Table 3). Trickey Pond was the only lake in which green algae did not make up
the majority of algae counted on average. Instead, diatoms made up 44% of samples on aver-
age and green algae accounted for 39%. Sand Pond and Trickey Pond had relatively high aver-
age levels of golden algae compared to the other lakes, mainly due to high Dinobryon counts.
The total number of algae cells counted in a particular lake fluctuated over time, though
there was no clear pattern in algae abundance across all lakes. The relative amount of algae in
each of the six categories also varied over time in each lake (Figure 1). The average number of
cells/mL in a sample was 155 cells/mL with a range of 92-234 cells/mL (Table 2). McWain
Pond and Highland Lake had the highest average levels of algae and Woods Pond, Hancock
Pond, and Trickey Pond had the lowest levels.
Figure 1. Graph showing changes in the relative amounts of different types of
algae in Hancock Pond between July and September of 2015.
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Results (continued)
Green Algae Cyanobacteria Diatoms Golden Algae Dinoflagellates Cryptomonads
AVERAGE 62% 16% 14% 7% 1% 0%
Hancock Pond 58% 10% 25% 3% 4% 0%
Highland Lake 77% 16% 6% 1% 0% 0%
Keoka Lake 82% 10% 4% 4% 0% 0%
Long Lake* 61% 16% 19% 4% 0% 0%
McWain Pond 57% 17% 18% 8% 0% 0%
Moose Pond (North) 69% 21% 7% 3% 0% 0%
Moose Pond (Main) 51% 40% 4% 5% 0% 0%
Peabody Pond 68% 18% 7% 7% 0% 0%
Sand Pond 59% 7% 13% 19% 2% 0%
Trickey Pond 39% 1% 44% 16% 0% 0%
Woods Pond 55% 32% 10% 3% 0% 0%
Table 3. Average percentage of each type of algae in each lake, as well as on average across all lakes. *Long Lake statis-
tics are an average of 1 sample from each of the three basins
Lake Average cells/ml Most Commonly Counted Genera
Hancock Pond 108 WestellaG, TetrasporaG, TabellariaD, TabellariaD
Highland Lake 234 WestellaG
Keoka Lake 215 WestellaG, WestellaG, WestellaG, DinobryonGO
Long Lake* 160 AsterionellaD, DinobryonGO, RhabdodermaG
McWain Pond 225 TabellariaD, TabellariaD, TabellariaD, TabellariaD
Moose Pond (North) 149 WestellaG, AsterionellaD, MerismopediaC, MerismopediaC
Moose Pond (Main) 151 WestellaG, MerismopediaC, MerismopediaC, AphanocapsaC
Peabody Pond 141 WestellaG, MerismopediaC
Sand Pond 156 TabellariaD, TabellariaD, DinobryonGO, DinobryonGO
Trickey Pond 118 AsterionellaD, WestellaG
Woods Pond 89 WestellaG, MerismopediaC, EucapsisC, TabellariaD
Table 2. Number of cells/mL counted in an average sample and most commonly counted algae genera in the samples
collected from each lake. Common genera are listed in chronological order of sample collection (first genus listed was
the most common in the first sample taken, etc.) (G = Green algae, C = Cyanobacteria, D = Diatom, GO = Golden algae)
*Long Lake statistics are an average of 1 sample from each of the three basins (North, Middle, and South).
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Discussion
The results of algae sampling in 2015 give LEA a baseline of algae conditions in 10
lakes over the months of July, August, and September. This baseline sampling is important be-
cause it provides a record of conditions to which future data can be compared. This data will
help in assessing changes over time and determining what a normal algae population looks like
in each lake. Because these lakes currently have good water quality, knowing which algae are
present, and in what concentrations, is especially important. Any water quality changes in the
future will he easier to assess if current water quality conditions are understood.
One of the main findings was that green algae were the most counted type of algae.
Green algae are certainly a diverse category, with about 2,400 freshwater species. Although
they are often counted, green algae do not generally contribute much to the biomass of algae
present in a lake. This highlights an important point—the number of cells/mL counted does not
correlate to the amount of algal biomass (or chlorophyll concentration) in a lake. This is be-
cause a large, relatively heavy single algae cell is counted as one cell, whereas a tiny colony of
algae may have all of its individual cells counted. The biomass (and chlorophyll levels) of the
tiny colony may well be lower than the one large algal cell, but the colony would contribute
much more to the calculated number of cells/mL. The unit of cells/mL does not measure cell
size or chlorophyll level. Therefore, we can’t directly compare the results from this study to
chlorophyll-a concentrations measured in the lakes tested.
Similarly, Table 2 shows that a number of the most common algae genera were not green
algae, despite the fact that green algae were the most counted group. This can also be ex-
plained by the diversity of the green algae. High green algae counts were often due to the com-
bined total of multiple genera, whereas other groups contributed less to the overall amount of
algae but were made up of only one or two genera. For example, in a sample with 100 green
algae and 20 diatoms, green algae are the most common group. However, if you look at the
genera that make up that sample, there may be 10 different types of green algae (10 of each)
but there is only one type of diatom, of which there are 20—making the most common genus
of algae a diatom.
Reported cell counts in low-nutrient lakes generally range from 0 to 1,000 cells/mL, alt-
hough there are no established guidelines that define lake status based on cell counts. Lakes
within this range are considered oligotrophic to oligo-mesotrophic. Average cell counts in this
study were low at an average of 155 cells/mL. While the lakes studied are low in nutrients, the
counts are probably underestimates based on reports from similar lakes. This likely has to do
with zooplankton grazing during holding times, and is in part due to the variability inherent in
the process of manually counting algae, which is affected by equipment and experience level.
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Discussion (continued)
The following are descriptions of ideal water conditions for the five most common gene-
ra found in the lakes tested. The dominance of these algae can be used to infer what lake water
quality conditions were like when the samples were taken. However, it should be noted that the
environmental preferences of individual species within these genera may differ. Information
presented are based on findings from Morabito and Curradi (1997) and Taylor et al. (1979).
Asterionella is a diatom which is found throughout the spr ing, summer, and
fall in low-nutrient lakes. It prefers cooler temperatures, high oxygen levels, and
high water clarity, and will be most common in lakes with those characteristics.
Dinobryon is a golden algae that is most common in the spr ing and fall, of-
ten after diatom population peaks. This genus is found in abundance in similar
conditions as Asterionella: cooler, low-productivity lakes with high clarity and
oxygen levels. They are also associated with high N:P ratios.
Merismopedia is a type of cyanobacter ia (blue-green algae). Its individual
cells are very small and form colonies, so although it is common in cell
counts, it has relatively low biomass. This genus is most common in summer
and fall. It is tolerant of low oxygen and low clarity conditions and higher
nutrient levels. It grows well in warm water and is associated with low N:P
ratios and higher lake productivity.
Tabellaria is a diatom that is found throughout the spr ing, summer, and
fall. It is common in low nutrient, clear waters with high secchi readings. It
often dominates in moderately acidic lakes with low alkalinity that also have
low phosphorus and chlorophyll levels.
Westella is a type of green algae that is associated with moderate nutr ient
levels and is tolerant of pollution and low pH levels. It can be found in the
spring, summer and fall, however it tends to dominate when lakes are unstrati-
fied or in stratified lakes with large mixing zones.
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Discussion (continued)
Many of the most common algae present when the lakes were sampled in 2015 are in-
dicative of good water quality. In addition, cyanobacteria levels were low in most of the lakes.
While it is difficult to draw conclusions based on only a couple of months of sampling, the
dominant algae and the percentage of cyanobacteria can be useful in making generalizations
about lake condition. Moose Pond’s main basin and Woods Pond had the highest average cya-
nobacteria levels. They were also two of the four basins (along with Moose Pond’s north basin
and Peabody Pond) where Merismopedia was the dominant genus in at least one sample. These
facts in and of themselves do not mean that these lakes are in trouble, but it means they are of
particular concern for further testing. Merismopedia is a very small colonial algae, so the
counts are often high even though there is relatively little of it present in terms of biomass.
These high counts then correlate to high percentages of cyanobacteria. The role that Merismo-
pedia (and the other algae identified) plays in the algae communities in these lakes will be-
come more clear once we have multiple years’ worth of algae data to compare with.
2016 Sampling
LEA will continue sampling algae monthly between May and September of 2016. Be-
ginning the sampling earlier in the season will help us better understand shifts in algae popula-
tions over time. We will also be able to compare samples from July, August, and September to
the samples taken in 2015 to gain insight into how populations may change from year to year.
We are also looking to increase and improve our algae identification capabilities. We are hop-
ing to get a microscope camera, which we will use to photograph unknown algae. This allows
us the flexibility to identify algae at a later date. The pictures can also be used to make an algae
identification guide unique to our lakes.
References
Morabito, G., & Curradi, M. 1997. Phytoplankton community structure of a deep subalpine
Italian lake (Lake Orta, N. Italy) four years after the recovery from acidification by lim-
ing. Internationale Revue der gesamten Hydrobiologie und Hydrographie, 82(4), 487-506.
Taylor, W. D., Hern, S. C., Williams, L.R., Lambou, V. H., Morris, M. K., and Morris, F. A.
1979. Phytoplankton Water Quality Relationships in U.S. Lakes. United States Environ-
mental Protection Agency.
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Acknowledgements
We gratefully acknowledge the help and support of the Portland Water District, who showed us
their filtering and counting methods and provided much assistance and advice with materials
and equipment.
Thank you to the following sponsors who helped to fund this project:
An Anonymous Foundation
Hancock and Sand Ponds Association
Keoka Lake Association
McWain Pond Association
Moose Pond Association
Peabody Pond Assocation
Residents of Woods Pond
Trickey Pond Association
Lastly, thank you to all LEA members: You made this project and all of LEA’s work possible.
11
230 Main Street
Bridgton, ME 04009
207-647-8580
Lakes Environmental
Association