Racine-Johnson Aquatic Ecologists

222 Pages·2008·19.28 MB·English

Aquatic Plant and Aquatic Macroinvertebrate
Monitoring in Chautauqua Lake during 2007

All Species Eurasian water milfoil

Racine-Johnson Aquatic Ecologists
Ithaca, NY 14850
Cover Abundance Maps
Robert L. Johnson

All Plant Species vs. Eurasian water milfoil in 2007

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Aquatic Plant and Aquatic Macroinvertebrate
Monitoring in Chautauqua Lake during 2007

Title Page

Prepared for the Chautauqua Lake Management Commission
Established by Chautauqua County
Mayville, NY

Submitted January 2008 by:

Racine-Johnson Aquatic Ecologists
1185 Ellis Hollow Road
Ithaca, NY 14850

Robert L. Johnson
[email protected]

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Executive Summary

In 2007, Racine-Johnson Aquatic Ecologists surveyed Chautauqua Lake for aquatic
plant (macrophyte) presence, abundance, and location. Additionally we surveyed
macroinvertebrate (animals without a backbone, and large enough to view with the unaided
eye) presence and location through a sub-contract with Christopher D. Ecker and Janis
Bowman of Jamestown Community College. Aquatic macrophytes and macroinvertebrates
play key roles in the ecology of lakes and this report provides a baseline to view historical and
future changes in Chautauqua Lake’s ecosystem. This is the product of a contract to evaluate
current aquatic plant and macroinvertebrate populations in Chautauqua Lake for Chautauqua
County’s Chautauqua Lake Management Commission.

Racine-Johnson Aquatic Ecologists sampled aquatic plants from 716 Chautauqua Lake
locations at least once in 2007 from June 13 – October 27. Additionally, to document
changes in the plant community caused by possible insect herbivory we sampled 120
locations once in June and then those same 120 again in September and October. Ecker and
Bowman collected macroinvertebrates in 2007 from a macrophyte sample, a dredge sample
and where possible, a shoreline sample at 45 Chautauqua Lake locations.

2007 Major Findings

1) In 2007, we identified 28 submersed or floating aquatic plant species by the rake-toss
sampling method at selected sampling points. The species richness (total species
found) of 28 compares well to the species richness reported to the Chautauqua Lake
Association in 2003 and 2004 by the Cornell University Research Ponds of 30 and 21
respectively. Similarly, two historical studies (Mayer et al. 1978) have similar species
richness in 1937 and 1972-1975 with 24 and 22 respectively (Table 2).

2) Analyzing the 716 sampled lake locations we recorded the percentage occurrence of
each individual species and found Myriophyllum spicatum at 72% of the locations
followed by Ceratophyllum demersum (47%), Zosterella dubia (43%), Elodea spp.
(41%), Najas guadalupensis (41%), Potamogeton pusillus (37%), Potamogeton crispus
(32%), and Vallisneria americana (28%) (Table 3). While assessing the presence of
aquatic plant species at all 716 locations in 2007 we note that there may be a bias
toward individual species due to greater numbers of sampled locations in the shallow
Mayville and Burtis Bay areas of the lake (Table 3, Figure 7, Appendices A, B).

3) Evaluation of the 2007 aquatic plant relative abundance measured as biomass or as a
rake-toss estimate at individual locations shows that the quantity of M. spicatum is not
always greater than an individual native species or all native species combined in 2007
(Tables 4, 6, Appendices A, B).

4) There appears to be no apparent trend when comparing temporal variability (year-to-
year changes) of species richness, plant biomass and abundance data in 2007 to earlier
data sets. Large variations that exist between the 2007 plant biomass and abundance
data sets and historical data prevent the identification of any directional trend (Tables 2,
5, Appendices C, D).

5) Contrasting spatial distribution (data from locations around the lake) of the 2007
abundance of plant species to a 2003 data set shows significant changes at specific
locations, but changes are not consistent for all locations (Table 6, Appendices B, D).
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6) Both surveys documented greater diversity of macrophytes and macroinvertebrates at
natural shoreline locations compared to locations near break walls (Appendices A, E,
F).

7) Our macroinvertebrate study identified 83 macroinvertebrate types in 2007 contrasted
to 64 types reported in the Erlandson survey completed in 1972-1974 (Mayer et al.
1978). The comparison excludes midge family genera. Of these 83 types, 49.4% were
insects, 25.3% were mollusks, 9.6% were leeches, 8.4% were segmented worms, 3.6%
were crustaceans, and 3.3% were miscellaneous types (Table 8).

8) The analyses of macroinvertebrate functional feeding groups at each of the 45 lake
locations identifying species presence and density suggest high variance among habitats
but may also be an indication of areas subjected to greater pollution (Appendices E, F).

9) Leach diversity increased 60% from seven in the Erlandson 1972-1974 study to 15 in
2007 (Table 8). This apparent increase in diversity suggests possible favorable benthic
conditions created by increased sedimentation from erosion, the exotic zebra mussel
Dreissena polymorpha, and / or changing macrophyte and fish communities.

10) Variation in macroinvertebrate diversity among lake locations may indicate that some
areas of the lake are healthy ecologically, possessing a strong diversity of pollution
sensitive organisms, and that other areas remain impacted by pollution, as indicated by
an increase in segmented worms at these sites (Appendices E, F).

Recommendations

1) Promote the healthy growth of low-growing native submersed plants along with a
variety of native emergent shallow water plants to reduce wave-driven turbidity, to
prevent the re-suspension of nutrients, and to create desirable macroinvertebrate
habitats.

2) Encourage increased macroinvertebrate populations and watermilfoil herbivory in
wide areas of the lake by limiting the interfering control measures detrimental to their
survival and population increases.

3) Monitor macrophyte and algae production, plant herbivores, and water quality
characteristics to be able to provide up to date information for improved aquatic
macrophyte and algae management.

4) Limit the flow of nutrients and soil into the lake by increasing focus on land use,
implementing watershed conservation measures and expanding tertiary treatment for
wastewater flowing into Chautauqua Lake.

5) Encourage residents with lakeshore property to limit fertilization and develop a
vegetative buffer zone of tall grass and shrubs between their lawns and the waterline.
Additionally, to further landscape their shallow-water areas with native emergent
aquatic plants, to reduce wave-driven erosion and the re-suspension of nutrients.

6) Conserve remaining natural shorelines and encourage replacement of concrete break
walls with more natural alternatives. Natural shorelines limit nutrient flows into the
lake and reduce in-lake wave velocity detrimental to near shore ecosystems.
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Contents
Title Page ................................................................................................................................... 3 
Executive Summary ................................................................................................................... 4 
Contents ..................................................................................................................................... 6 
Figures and Tables List .............................................................................................................. 7 
Introduction ................................................................................................................................ 9 
Specific aquatic plant monitoring Section ............................................................................... 11 
Methods ........................................................................................................................ 11 
Results and Discussion ................................................................................................. 13 
References .................................................................................................................... 31 
Chautauqua Lake 2007 Macroinvertebrate Biodiversity Assessment Section ........................ 34 
Summary ...................................................................................................................... 35 
Introduction .................................................................................................................. 35 
Methods and Materials ................................................................................................. 37 
Results and Discussion ................................................................................................. 42 
Conclusions .................................................................................................................. 47 
References .................................................................................................................... 48 
Appendix .................................................................................................................................. 49 

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Figures and Tables List

Figure 1a. Example of 100m X 100m map grid of the UTM coordinate system
showing plant species richness (number of species recorded at each
intercept of two lines) at locations sampled south of Prendergast Point
and north of Whitney Bay……………………………………………………….....11

Figure 1b. Macrophyte sample collected with dual headed rake…….……….……………….12

Figure 1c. Separating rake sample of macrophytes to species for % estimate...................…..12

Figure 2. Best fit line to describe the relationship between estimates made with
the rake-toss method and biomass measures made at the same locations
and time in 2007…………………………………………………………………...16

Figure 3. Map reproduced by photo from IT Corporation, 1988-1989, Chautauqua
Lake final report 1988-1989 water and sediment monitoring bathymetry
and macrophyte mapping for August 1989………………………………………..25

Figure 4. Map reproduced by photo from IT Corporation, 1988-1989, Chautauqua
Lake final report 1988-1989 water and sediment monitoring bathymetry
and macrophyte mapping for November 1989…………………………………….26

Figure 5. Map showing macrophyte abundance of all plant species combined in
the south basin in June 2007…………………………………………………….…27

Figure 6. Map showing macrophyte abundance of all plant species combined in
the south basin in Fall 2007………………………………………………………..28

Figure 7. Macrophyte species richness map showing total number of species found
at each location in the south basin by the rake-toss method in June 2007……..….29

Figure 8. Macrophyte species richness map showing total number of species found
at each location in the south basin by the rake-toss method in Fall 2007…….…...30

Figure 9a. 2007 macroinvertebrate sampling sites in Chautauqua Lake’s south basin…….…38

Figure 9b. 2007 macroinvertebrate sampling sites in Chautauqua Lake’s north basin…..…...38

Figure 10. Benthic comb used in Chautauqua Lake in 2007 to sample aquatic
macrophytes for macroinvertebrates………………………………………….…...40

Figure 11. Ekman dredge used in Chautauqua Lake in 2007 to collect lake-bottom
samples for macroinvertebrates……………………………………………………40

Figure 12. Mesh bucket used in Chautauqua Lake in 2007 to rinse lake-bottom
samples when collecting macroinvertebrates……………………………………...41

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Figures and Tables List

Figure 13. Sweep net used in Chautauqua Lake in 2007 to collect macroinvertebrates
from macrophytes……………………………………………………………….…41

Figure 14. Trophic food web depiction of stored energy. Energy gradually decreases
in the direction of the arrow………………………………………………………..46

Table 1. Abundance categories used to describe rake-toss samples and the assumed
mean dry weight values (g / m2) and ranges used in spreadsheet processing
of field data (Appendix B) to obtain an estimate of abundance for
individual species or grouping of species.…………………………….…………...12

Table 2. Aquatic plants, including vascular plants and macro-algae, identified in
Chautauqua Lake in 1937 and 1972-75 using field reconnaissance, and
2003, 2004, and 2007 using the rake-toss method………………………………...14

Table 3. Aquatic plant species found in Chautauqua Lake during 2007 rake-toss
sampling. Number of locations refers to the number of sample points
where we found each individual species out of the 716 possible locations
(excluding the second sampling locations)…………………………………….…..15

Table 4. Biomass of aquatic macrophytes at selected locations in 2007 sampled
with five randomly selected 0.25m2 quadrats at each location and
expressed as g / m2 dry weight……………………………………………………..17

Table 5. September comparisons of 1981-89 biomass data recalculated from
Luensman et al. 1990 to biomass in 2007 expressed as g / m2 dry weight………….21

Table 6. Change in estimated abundance categories from 2003 to 2007 for all
aquatic plants and selected individual species. The selected species
are Eurasian water milfoil (Myriophyllum spicatum), elodea
(Elodea spp.), coontail (Ceratophyllum demersum), water stargrass
(Zosterella dubia), naiads (Najas guadalupensis and Najas flexilis),
leafy pondweed (Potamogeton pusillus), and curly leaved pondweed
(Potamogeton crispus)……………………………………………………………..22

Table 7. Latitude and longitude coordinates for 2007 Chautauqua Lake
macroinvertebrate sampling sites (Figures 9a, 9b)………………………………...39

Table 8. Macroinvertebrates collected from Chautauqua Lake, June 3 - August
27, 2007……………………………………………………………………………43

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Introduction

This report presents the results from a 2007 survey of submersed and floating aquatic
plants (macrophytes) conducted by Racine-Johnson Aquatic Ecologists in Chautauqua Lake.
Additionally, a survey of macroinvertebrates (animals large enough to be seen with the
unaided eye but lacking a backbone) made by Christopher D. Ecker and Janis Bowman of
Jamestown Community College in 2007 is part of this document. Both surveys relate current
information to historical data to assess changes. This report documents the present status of
macrophytes and macroinvertebrates in Chautauqua Lake with our findings and suggested
recommendations for consideration by all Chautauqua Lake’s interest groups wanting to
improve their lake ecosystem.

Chautauqua Lake’s littoral zone (the shallow water from the shore to the depth where
macrophytes no longer root) covers large areas of the lake especially at the shallow north and
south ends. The lake, a nutrient rich water body, has a long history from the 1800’s to the
present as the premier warm-water sport fishery in New York State (Bimber and Nicholson
1981, Mayer et al. 1978). Competing with the fishery is the many faceted recreational and
aesthetic demands on the lake’s resources. This demand to manage the lake for multiple uses
inherently focuses on the control of macrophyte growth. The macrophyte community in the
shallow and fertile Chautauqua Lake remains a primary stabilizing force to maintain a healthy
freshwater ecosystem (Johnson et al. 2005). They not only provide the obvious benefit of
habitat for macroinvertebrates reported in the second part of our 2007 survey, but also for
amphibians, fish, and birds. The macroinvertebrate section of this report reinforces the close
link of invertebrate diversity and density with macrophyte presence, abundance and diversity.

The aquatic plant community in Chautauqua Lake is essential to the health and
existence of this very important freshwater ecosystem in Chautauqua County. The residents
of, and visitors to, Chautauqua County consider the lake and surrounding area as the
economic engine for the region because of its quality of life, aesthetic contributions, tourism
and recreational opportunities, and of course the premier warm-water fishery. Many have
emphasized historically (Luensman et al. 1990, Nicholson 1981) and recently (Johnson et al.
2006, Johnson et al. 2005, Wilson et al. 2000), the importance of a vibrant submersed aquatic
plant community in Chautauqua Lake to the future existence of this irreplaceable resource.

The community also struggles with the question of how to manage the multiple public
expectations for this resource. The management of aquatic plant growth in Chautauqua Lake
has always been the focal point attempting to address public concerns about water quality.
This will likely remain at the top of lake management issues in the near future. We hope this
report of data accumulated from routine scientific monitoring will be an additional step
forward adding to previous studies, which will allow informed management decisions for the
Chautauqua Lake ecosystem.

The primary method of monitoring aquatic plant macrophyte growth for this study was
the rake-toss method explained in the following methods section. This method, used by the
Cornell University Research Ponds since the late 1980s, underwent a slight modification by
adopting the use of UTM coordinates and grid sampling (Madsen 1999). Since 2000, Cornell
University Research Ponds has further expanded and refined their methodology. NYSDEC
will likely require a similar method of measuring macrophyte presence and growth in New
York State lakes to evaluate the efficacy of aquatic macrophyte management techniques
conducted on “high profile” lakes in New York. This likely will be part of the permitting
process required in the future when applying for a permit to treat a “high profile” water body
in New York State with a herbicide for plant control.
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Chautauqua Lake has a nearly comprehensive set of survey data from studies conducted
by rake-toss starting in 2003 and 2004 when Cornell University Research Ponds monitored
large areas of the lake under contract with the Chautauqua Lake Association (Johnson et al.
2005, Lord et al. 2004). That data is included here for easy access and comparison
(Appendices C, D). The Cornell University Research Ponds work for the Lake Association
also details the contribution of water milfoil herbivores to overall aquatic plant management
in the Chautauqua Lake ecosystem (Keith et al. 2007, Johnson et al. 2006, Johnson et al.
2005, Lord et al. 2004, Johnson and VanDusen 2003, Johnson and Blossey 2002).

Our on-lake macrophyte survey detailed in “MS Excel” spreadsheets (Appendix B) and
depicted on maps, (Figures 5 - 8, Appendix A) in this report measures species presence and
abundance with an emphasis on locations of public concern. Many of our sampled locations
are beyond the shore areas mechanically harvested and we feel the influence from the
harvesting operations on our results is minimal. This allows us to make comparisons to
earlier historical macrophyte data and infer possible changes with confidence. We included
complete data files of previous rake-toss surveys in 2003 and 2004 conducted for the
Chautauqua Lake Association by the Cornell University Research Ponds. Inclusion of this
data collected by similar methods to the 2007 survey will allow easy access to future data
comparisons.

We discuss the use of air photos as a method that appears to be relatively simple and
time saving. This report includes macrophyte maps from a comprehensive 1988 and 1989
lake report by IT Corporation 1989 using air photos. However, the method has several
important limitations with the 1989 report suggesting, “Aerial photography as a macrophyte
mapping technique is probably more useful for identifying areas of the lake experiencing
severe macrophyte growth”. The maps show in 1989 that the littoral zone is for the most part
covered with Eurasian water milfoil in August and more so in November. It appears to be
compelling when the plants break the surface or are at the surface. This works well to show
plant coverage that breaks the surface, but not coverage or individual species in years when
the plants do not reach the surface.

The most reliable information still appears to be data gathering on the water with
proven scientific methods of data collection. Dry biomass measures for estimating aquatic
plant growth still gives the best information. The use of the rake-toss method on this project
allows the collection of considerable information over large areas. It allows for the use of a
very powerful tool of actually “looking” under the surface of the lake and measuring what is
there at any one time. An example is the relative abundance maps and rake toss data sheets
that allowed the production of the maps.

One last consideration, for those with the power to influence the future of the
Chautauqua Lake ecosystem, would be to increase the landscaping of the very shallow water
areas along the shoreline. This idea prompted by questions to me at unrelated times this past
year by the two top officials of the Chautauqua Watershed Conservancy. At a public forum,
the question to me was “is there a plant that would grow along the shoreline, in the water, to
stabilize this area always in turmoil”. Although that same idea had crossed my mind before
while on Chautauqua in a heavy wind with the waves crashing on the shoreline, I did not have
a good answer. The second question came a few weeks later when asked to identify a plant in
the lake from a photo. I went to the location where the photo was taken and collected
specimens and later found the plant species, Justicia americana (L) Vahl, [=Dianthera
americana L] a native emergent in another area of the lake doing just what we would desire,
stabilizing the shore. Consideration of this plant and other native species for the task of
reducing shoreline erosion and nutrient uptake is essential.
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