state of the lake 2009
Lake Keeper Report
Final Report For 2009
Marine Study Program by Don Mayland
- A Description of the Physical, Biological and… Section 1
- The Lake Keeper Program Section 2
- Water Quality Data Section 3
- Discussion of the State of the Lake 2009 Section 4
This report is divided into 4 sections. Section 1 is a description of the physical, biological and geological characteristics of Lake Wononscopomuc and its watershed. I have borrowed extensively from the work of the Hotchkiss Summer Program (Portals) 2nd year environmental students. In July they carried on research into the trophic condition of the lake. They concluded their work by writing a Lake Wononscopomuc Management Plan. I have also used a considerable amount of the information published in the Natural Resource Inventory of the Town of Salisbury. The information in the Lakes and Streams section of this report was researched and written by Lynn Meehan and Barbara Niles.
Section 2 of this report is an explanation of the “Lake Keeper” program. This program was initiated by the Lake Wononscopomuc Association during the late winter and early spring of 2009. Marine Study Program, Inc. was hired to carry out the responsibilities outlined by the Association. The Lake Keeper program is funded in equal amounts by The Town of Salisbury, The Hotchkiss School and the Lake Wononscopomuc Association.
Section 3 is a statistical presentation of the sampling that was carried out from the time that ice left the lake in the spring to the period of the fall “turnover”. Sampling was carried on by Don Mayland, Chris Oostenink and Gabriel Haddon. The Science Department of the Hotchkiss School provided the necessary equipment to sample visibility, dissolved oxygen, temperature, conductivity and zoo and phyto plankton. In addition the School made their 19’ research vessel available for use in taking periodic samples. Water samples were sent to the Institute of Ecosystems Studies (IES) in Millbrook, NY to determine phosphorus content. A special thanks must go to Denise Schmidt, Laboratory Manager at IES, for her work in providing the data from these samples. I also owe a special thanks to Chris Oostenink. His expertise as a biologist and limnologist were of tremendous value in interpreting the data that was collected.
Section 4 is a summary and discussion of the 2009 condition of the lake. This discussion will be an interpretation of the data about oxygen levels, phosphorus levels, visibility and changes in the weed growth during the 2009 season.
I have also included an appendix, which contains a map of the watershed of Lakeville Lake and a listing of the owners of parcels of land within the watershed. A second appendix is the Lake Management Plan which the Portals Summer School students constructed.
A Description of the Physical, Biological and Geographical Conditions of Lake Wononscopomuc and its Watershed
Lake Wononscopomuc, better known as Lakeville Lake, is completely contained within the Town of Salisbury and the Village of Lakeville. It is the deepest natural lake in the State of Connecticut, reaching a maximum depth of 106 feet. The lake is divided into two distinct basins. The deep basin n is located in the western portion of the lake. It is separated from the shallower basin by a ridge which, in places, is only 10 feet below the surface. The shallower basin reaches a maximum depth of 60 feet and is located in the northeast portion of the lake. On average the lake has a depth of 36 feet. The lake covers 353 acres. The watershed of the lake covers only 1621 acres. A detailed watershed map is presented in Section 4 of this report. The watershed includes the drainage from Belgo Hill and Sucker Brook. Surface water flows feed the lake from one perennial stream (Sucker Brook) and two unnamed intermittent streams. Numerous underground springs also provide water to the lake. I have included as an addendum to this report the Lake Wononscopomuc Management Plan which the Hotchkiss second year summer school students wrote in July 2009. This plan contains a detailed description of the lake’s history and geography. There is little point in my simply rewriting the excellent work that these students did.
The Lake Keeper Program
Lake Wononscopomuc, like all lakes, is aging. Aging is evident in water quality changes, changes in weed growth, changes in fish populations and zooplankton and phytoplankton changes. The aging process is inevitable. However, human activities can cause a dramatic speeding up of the process. Increased development of lakeshore properties and properties in the small watershed of the lake can be a source of nutrient input into the lake. In the past twenty five years the lake has suffered “invasions” of plants like Eurasian Milfoil and an algae called Ocillatoria Rubecens. Other invaders are close; Zebra Mussels are well established in both of the Twin lakes and the Housatonic River and Hydrilla and Brazilian Elodea are in neighboring Connecticut and New York lakes. The lake association is determined to establish a monitoring program that will provide early warning about the arrival of any of these types of “invaders”.
The Lake Keeper program has several objectives. Monitoring water quality and monitoring invasive species of plants and animals are clearly two of the main objectives, but they are by no means the only ones. Another objective of the 2009 program was to map the watershed of the lake and to compile a list of property owners within the boundaries of the watershed. Enlisting the cooperation of these property owners will be a long term process and a very necessary one. Nutrient input from fertilizers, roof and driveway run off and septic tanks is a major threat to the present and future health of the lake.
A third component of the keeper program is to provide educational opportunities for property owners and residents, recreational users of the lake and students in the area.
Water Quality Data
The Lake Keeper program is certainly not the first effort at measuring the water quality of Lakeville Lake. Many studies have been conducted that presented data on the water quality of the lake. However, the Keeper program is the start of an effort to provide a continuum of data over time. Sampling of the water was done on a weekly or monthly basis soon after ice was out until the end of the fall turnover in November.
Wherever possible I have compared the data collected this year to the data presented in earlier studies. The studies that I am referring to are the following:
- A study by Dr. Richard Miller of the Union Carbide Corp. in 1977
- The sampling done by Ted Davis(Hotchkiss Limnologist) in the 1980s
- The sampling done by Greg Bugbee(CT Agricultural Experiment Station) in the fall of 2003
- A study of the trophic Conditions of the lake by Dr. Nina Caraco in 2006
The sampling that I did was at three stations (buoys) in the lake. The first (buoy A) is located in front of the Hotchkiss waterfront in about 60’ of water. The second is the buoy (buoy B) that marks the deep hole in the lake. The depth is approximately 106’ at this buoy. The third is the buoy (buoy C) that marks the intake of the old hypolimnetic pumping pipe, located in front of the Town Grove. The depth at this buoy is approximately 55 ‘.
Sampling was done at each buoy at depths of 10’(3.05m), 30’ (9.2m)and 50’.(15.3m) In addition at buoy B a fourth sample was taken near the bottom(approximately 95’ of depth).(28.97m)
At each buoy and at each depth the following data was gathered:
- Dissolved Oxygen (MG/L and %)
- Total Phosphorus (sampled 4 times during the 2009 field season)
Every effort was made to do the water quality sampling at the same time of day and in the same weather conditions each day that I went out on the lake. Generally, sampling was done between 10:00AM and 11:00 AM and the weather was sunny with little wind.
Temperature readings were obtained by using the following probe: YSI manufacturer, Model 550A.
Weather during the 2009 sampling season was exceptionally rainy and cool. The only 90 degree (F) or above temperatures were recorded during April. This persistent cool weather meant that the thermocline did not drop to the 28’ (8.54m) depth that is typical in mid-summer. The deepest thermocline reading was at a depth of 24’. (7.32m)
All temperature readings are in degrees Celsius
Discussion of the State of the Lake 2009
The Lake Keeper program will have value over time as an early warning system of changes that are occurring in the lake water quality and the surrounding watershed. However, it will take time and several years of data to put this system into place. One season of data collection cannot detect major changes to the trophic state of the lake that could be occurring because of outside factors. Several years of data, however, can be very precise in exhibiting these changes. The 2009 season is a start.
Care was taken to sample water quality periodically during the April to November open water season under conditions that were similar, if not identical. All of the sampling was done in the morning between the hours of 10:00AM and 11:00AM. Every day, with one exception in November was sunny with little wind. The same instruments were used to collect data on each day of sampling.
The summer of 2009 was not a typical summer in terms of temperature or rainfall. Therefore, the data about water temperature may vary from the norm. The warmest air temperatures of the sampling season were experienced in mid and late April . Summer air temperatures tended to be lower than the norm. The thermocline is the layer of water that separates the warmer water above (the epilimnion) from the colder water below. (the hypolimnion) In Lakeville Lake it usually sets up by mid April, initially at a depth of about 12’. As the season progresses the thermocline will typically sink to a depth of about 28’. The thermocline during the 2009 sampling season was around 24’ until very late in the season, when it dropped to the 35’ to 40’ level.
The following is a temperature profile conducted on October 29, 2010:
|Depth (ft)||Temperature (C)|
Surface temperatures during the season showed a typical trend, reaching the highest in early August and then dropping off by the end of the month. Ice began to form on the lake by mid December and the lake was frozen over by January 9, 2010.
Visibility in the lake during the sampling season was reduced. There were several reasons for this. One was the large amount of rainfall in the spring and early summer. A second was the “whiting” that occurred in July and a third was a larger than normal phytoplankton population.
Chris Oostenink, a Limnologist with the Hotchkiss School and a consultant to Marine Study Program, Inc. provides the following explanation of a “whiting”.
The precipitation of colloidal calcite(CaC03) is a common phenomenon in hard water lakes.
It is brought about by a reduction in the amount of dissolved carbon dioxide (CO2) in the water.
The reduction in CO2 is caused by two things:
- as the water warms up the solubility of any gas is reduced, so CO2 concentration is limited, and
- as the summer goes on photosynthesis by rooted plants and floating phytoplankton consumes large quantities of dissolved CO2.
So, what you have is a very natural situation that is common in lakes where the watershed geology
is like ours. The particles of calcite are so small that if you scoop a glass of water out of the lake it
appears perfectly clear, they only are able to impact the clarity of the lake as profoundly as they do
because of the large volume involved in the lake wide. Furthermore, because the particles are so
small they take a very long time to settle out of the water column…….
The “whiting” phenomenon has occurred during several summers in the recent past. There seems to be no correlation between “whiting” occurrences and the trophic state of the lake.
The phyto plankton population in the lake, observed during the summer months, is far more troubling. A preliminary identification of the algae that was present during the summer is that it is a type of cyanobacteria called Gloeotrichia Echinulata. This is a type of algae that is commonly found in mesotrophic and eutrophic lakes in the northeastern part of the country. It begins forming colonies during the early summer , having acquired necessary phosphorus from the bottom sediment. According to King and Laliberte (May, 12, 2005) ,in a paper that they wrote about the algae in Maine lakes, Gloeotrichia E. can progress from little or none present in the plankton community in one year to “complete dominance” in the following season. The high phosphorus load in the bottom sediment in both basins of Lakeville Lake makes Gloeotrichia a real threat to the clarity of the water and the health of the lake. Increased monitoring of this situation should clearly be a high priority of the monitoring program.
Dissolved Oxygen in the water column was measured in two ways; level of saturation(%) and mg/l. Cold water can hold more oxygen than warm water. The colder water during the sampling season is at depths below 30 feet. However, % figures are much lower in the deeper water (hypolimnium) at all three sampling sites. While it is true that cold water can potentially hold more oxygen than warm water it is also true that there is a lot less oxygen in the deep water of the lake than in the upper layer (epiliminium). This can be readily seen by referring to the mg/l figures.
The dissolved oxygen numbers (mg/l) became very low near the lake bottom at all three sampling sites as the summer progressed. Most fish life cannot survive at oxygen levels below 5 to 6 mg/l. The anoxic situation in the deep water became very apparent by late July, as the data indicates. In addition, the hydrogen sulfide smell coming from the sensor was very pronounced. Hydrogen Sulfide is produced as a by-product of the decaying action of anaerobic bacteria.
The deep water (hypolimnium) of the lake has two very measureable problems. One is the lack of oxygen to support large cold water fish life, such as lake trout. A second problem is the phosphorus load in the bottom sediment. This phosphorus load (internal loading) supports nuisance algae growth, such as Gloeotrichia E.
When bottom waters (hypolimnium) become anoxic phosphorus gets released from the sediment. This internal loading is typically a major source of phosphorus in the water column. As the data above indicates, Lake Wononscopomuc bottom water becomes anoxic by mid-summer. It is not surprising, therefore to also see that the level of total phosphorus in solution in the bottom water also goes up late in the summer and into the fall. However, the level of phosphorus in the summer of 2009 did not come close to the very high level that was recorded in August of 1976 by Dr. Richard Miller in the original study done of the lake by Union Carbide. The highest phosphorus levels in 2009 were recorded in November. Internal phosphorus loading can promote algae growth such as Gloeotricia E.
Phosphorus also enters the lake from feeder streams and runoff from the land surrounding the lake. In May samples were taken from Sucker Brook and the small seasonal brook that comes down from The Wake Robin Inn and passes through the Floyd property. Fortunately, both of these showed low phosphorus levels. Sucker brook had a reading of .015 mg/l and the Floyd runoff was .003 mg/l.
Continual monitoring of both internal phosphorus loading and external sources is an essential part of Lake Keeper program, as future development in the watershed is a potential source of increased external loading of phosphorus .
PH and Conductivity:
Pure water is a poor conductor of electricity. Therefore, the higher the conductivity reading the more the total dissolved solids (TDS) and ions (a product of salinity)in the water column. Heavy rains with runoff from the land surrounding the lake will cause high conductivity readings. The readings that were recorded during the summer of 2009 were somewhat higher than those of Ted Davis in the summer of 1980, but given the amount of variables that can cause this, little should be read into this data. As conductivity is monitored on a more regular basis the significance of these readings will become more important.
Ph tells how acidic or basic water is. A Ph reading of 7 indicates neutral (neither acidic nor basic). The geology of the lake basin and surrounding watershed causes Lake Wononscopomuc to be quite basic. Limestone contains carbonate which contributes to alkalinity.
There does seem to be a real discrepancy between the Ph readings obtained during the summer of 2009 and that which was obtained by the Ct. Agricultural Experiment Station in September of 2005. However, the data of Ted Davis in the summer of 1990 is very similar to that obtained this past summer. Major changes in Ph readings over time are an indicator of the conditions that organisms living in the lake are experiencing. Ph is also related to plant populations and photosynthesis. CO2 removal reduces the acidity of the water and Ph increases. Since Ph is closely related to plant photosynthesis the time of the day (or night) can be a critical factor in the readings obtained. Monitoring of Ph on a regular basis at specified times of the day need to be a future goal of the Keeper program.
Weed Growth and Harvesting
There was a very noticeable reduction in the population of Eurasian Milfoil during the spring, summer and fall of 2009. This is not the first time the lake has experienced such a “crash” in the Milfoil population. The first time was during the summers of 1992 and 1993. There was a second “crash” in 2002 and now we are having a third. The cause of this decline in Milfoil is the larvae of the Caddis Fly. During the 1993 crash divers observed that the leaf structures of the Milfoil plants were being eaten by Caddis Fly larvae. It was also observed that the Caddis Fly larvae population in the lake was unusually large at that time. This high population density lasted about two years, which corresponded directly with the length of the Milfoil crash. In 2002 the same phenomenon was observed. It also lasted two years. Now, in 2009 the same situation has occurred. During the fall of 2008 it became very apparent that the Caddis Fly larvae population had once again become very large and dense in certain areas of the lake, especially along the lake shore. Now in 2009 we have witnessed a dramatic reduction in the Milfoil beds along the lake shore, especially along the NW shoreline, the Hotchkiss shoreline and the Town Grove area. During the summer of 2009 divers again observed the Caddis Fly Larvae eating the leaves and stems of the Milfoil plants. Unfortunately, the population of Caddis Fly Larvae was greatly reduced by the fall of 2009.
Milfoil seems to be the weed of choice for the Caddis Fly larvae, but it is not the only plant they eat. They will turn to Broadleaf Pondweed and Curly Leaf Pondweed once they have consumed all of the Milfoil in a particular locale.
When Milfoil density does go down other aquatic plants are quick to take over. Unfortunately invasive plants such as Curly Leaf Pond Weed often fill the spaces left open by the lack of Milfoil. Curly Leaf can be as big a problem, in terms of plant densities and matting on the surface, as Eurasian Milfoil. The good news about Curly Leaf is that it flowers on the surface in June and by mid July it has pretty much died back. Curly Leaf Pond Weed was very evident in the shoreline areas vacated by Eurasian Milfoil during the early summer of 2009.
The Lack of Eurasian Milfoil, especially along the NW shoreline enabled populations of Elodea (Northern waterweed), Common Naiad (Najas flexsilis) and Coontail (Hornwort) to establish them. In the Town Grove swim area and around the swim lanes these weeds, in addition to Chara (Stonewort or Muskgrass), became very evident by mid-summer. As weed populations change, due to the Milfoil crash, it is very important to continue to identify the plants to get an early warning of any invasive species that could be equally, or even more, troubling to the lake as Milfoil has been. Hydrilla and Brazilian Elodea are two such plant species that could be very troubling if they establish populations in the lake. Weed populations were sampled on five occasions during the summer of 2009. No Hydrilla or Brazilian Elodea plants were found, although distinguishing them from Elodea (Northern Waterweed) can sometimes be challenging. The growing populations of Chara and Tape Grass actually provide excellent competition to Milfoil as these are low lying plants that tend to carpet the bottom. The lack of Milfoil and the increasing populations of competitor plants meant that weed control barriers at the Town Grove Swim area did not have to be installed.
The weed harvesting program that is jointly funded by the Town of Salisbury The Lake Wononscopomuc Association and The Hotchkiss School also was scaled back during 2009 because of the decline in Milfoil, especially along the shorelines. Charles Ouellette, who conducts the weed harvesting, reported the following: In 2008 we removed 235 loads during the first cutting and 131 loads during the second cutting. In 2009 198 loads were removed during the first cutting and 49 loads during the second. This lack of milfoil was reflected in a substantially reduced charge for the cutting program.
During the early summer months a large population of algae was evident underwater in depths ranging from 5 feet to 15 feet. This alga appeared as large masses of green scum, lying near the bottom. As gases built up in these masses they rose to the surface, where they became unsightly. Wave action usually broke the masses apart and the algae then disappeared. By late July no masses of this alga could be found. I identified the alga as Spirogyra (Water silk), but this identification may not be accurate. A firm identification of this alga should be a goal to accomplish during the 2010 season as it has appeared during several preceding summers.
Marine Study Program, Inc. conducted four dives during the summer of 2009 specifically to look for Zebra Mussels. These dives were conducted on the ”wall” in the center of the lake, along the Town Grove waterfront, along the Hotchkiss waterfront and in the NW corner of the lake. No Zebra Mussels were found at any of these locations.
Bathing Water Sampling at the Town Grove:
The indicator organism used for monitoring bathing water is E. coli bacteria. A concentration of E. coli organisms greater than or equal to 235 per 100ml of water is considered unsatisfactory. The Torrington Area Health District sampled the water at the Town Grove on May 31, 2009, on June 20, 2009 and again on July 18, 2009. The highest count of E. coli they obtained was 53 per 100ml. This was on July 18, 2009.
A detailed map of the Lake Wononscopomuc watershed was constructed, using GIS technology, by the Housatonic Valley Association. This map not only shows the boundaries of the watershed but it also delineates each parcel of land by town tax number. A list of individuals who own property in the watershed was constructed. This map and the listing of property owners are available for viewing at the Salisbury Town Hall and by contacting the Lake Wononscopomuc Association. The map and property listings will be a valuable tool for future planning and communication.
Future development in the watershed will be a threat to the health of the lake if it is not monitored and managed properly. If recent trends continue larger year round houses will replace the current seasonal homes that still exist. This could mean increased land coverage by roof lines and paved driveways, in addition to larger square footage of homes. Removal of native lakeshore vegetation may also become a problem as land is “landscaped” to the tastes of homeowners. In addition, as development proceeds, larger septic systems and increased uses of fertilizers can occur. All of his means a greater possibility of external loading of phosphorus into the lake.
Lake Wononscopomuc attracts a diverse bird population. Bald eagles, osprey, great blue herons and even transient Loons could be found on the lake during the ice out period in 2009. During the late fall the gull population, mainly ring billed gulls, and the Canada Geese population was larger than the preceding few years. This was probably due to the fact that ice cover occurred on Lakeville Lake later than on neighboring water bodies, with the exception of the Housatonic River. The lake association does attempt to prevent the nesting of Canada Geese in the spring whenever possible.
The summer of 2009 also saw an increase in the population of double breasted cormorants. These birds, while interesting, can be troubling for a lake environment. Catherine Frank and Margaret Holden, in their book, A kayakers Guide to Lake Champlain(2009, Black Dome Press), describe what cormorants have done to one of the Four Brothers Islands in Lake Champlain:
Island D looks like a crowded marina, because its leafless, almost branchless
bare tree trunks stick up like masts. These trees supported twenty-two great
blue Heron nests in 2006, but today cormorants occupy every other limb.
Cormorants are extremely adaptable and will start to nest on the ground when tree space is gone. Their guano has been shown to be very damaging to native vegetation, which is why trees begin to look like boat masts.
The Population of cormorants on Lake Wononscopomuc, while not large, has begun to increase. In the start of the summer a pair of the birds was frequently spotted. In September the number was over 10. This situation should be carefully monitored.
The data collected during 2009 indicates that the trophic state of Lake Wononscopomuc is mid to late mesotrophic. Clarity was reduced because of unusual rainfall conditions, the occurrence of a “whiting” in July and a large phyto plankton bloom later in the summer. Threats to the health of the lake continue to be the low level of dissolved oxygen at the bottom of both basins in mid to late summer, the internal phosphorus loading from the sediments at the bottoms of the two basins, invasive plant and animal species and development in the watershed that could add to external phosphorus loading. The Lake Keeper program will provide a baseline, over time, to monitor trends in these health determining factors of the lake.