Great Sacandaga Lake 2007
Final Report
January 8, 2008
Author
Michael J. De Angelo
Project Participants
Michael De Angelo, environmental chemist
Lisa De Angelo, technician
Prepared by:
The Adirondack Watershed Institute Aquatics Division at Paul Smith's College
P.O. Box 244, Paul Smiths, NY 12970-0244
518 327-6270; fax: 518 327-6369; email: mdeangelo@paulsmiths.edu
world wide web: http://www.paulsmiths.edu/aai
Introduction
The purpose of this document is to present the results for the Adirondack Watershed Institute lake sample collection and water quality testing on Great Sacandaga Lake over a five month period during 2007. The results also include samples collected by a volunteer monitor for The Adirondack Lake Assessment Program. This is a volunteer monitoring program established by the Residents' Committee to Protect the Adirondacks (RCPA) and the Adirondack Watershed Institute (AWI). This combined sampling program was designed to expand on the usual water quality data that is collected every summer for Great Sacandaga Lake as outlined by the Darrin Freshwater Institute.
Methodology
Samples were collected at Sinclair Point by the Adirondack Watershed Institute over a five month period during the 2007 field season and over a two month period May and October at a second station, the Narrows, which was sampled the other three months by a volunteer monitor with the Adirondack Lake Assessment Program. The volunteer monitor then sent their samples to the Adirondack Watershed Institute for analysis.
AWI staff samples were collected at depths of 1.5 meters from the surface (epilimnion) and within 1.5 meters of the bottom (hypolimnion) for chemical analysis. A 2-meter composite of lake water was collected for chlorophyll-a and peugeon analysis. A secchi disk transparency, a dissolved oxygen and temperature profile was also performed at each station by AWI staff. Once collected, samples were stored in a cooler and transported to the laboratory at Paul Smith's College.
A volunteer monitor with the Adirondack Lake Assessment Program sampled the Narrows station for three months during the summer of 2007. This volunteer monitor (trained by AWI staff) measured transparency with a secchi disk and collected a 2-meter composite of epilimnion lake water for chlorophyll-a analysis and a separate 2-meter epilimnion composite for total phosphorus and other chemical analyses. The volunteer filtered the chlorophyll-a sample prior to storage. Both the chlorophyll-a filter and water chemistry samples were frozen for transport to the laboratory at Paul Smith's College.
All samples were analyzed by AWI staff in the Paul Smith's College laboratory using the methods detailed in Standard Methods for the Examination of Water and Wastewater, 21st edition (Greenberg, et al, 2005). Results for 2007 are presented in Appendix A. Some of the results will be highlighted and discussed in the following sections.
Note: Results are presented as concentrations in milligrams per liter (mg/L) or its equivalent of parts per million (ppm) and micrograms per liter (mg/L) or its equivalent of parts per billion (ppb).
1 mg/L = 1 ppm; 1 mg/L = 1 ppb; 1 ppm = 1000 ppb.
Results Highlights
pH
The pH level is a measure of acidity (concentration of hydrogen ions in water), reported in standard units on a logarithmic scale that ranges from 1 to 14. On the pH scale, 7 is neutral, lower values are more acidic, and higher numbers are more basic. In general, pH values between 6.0 and 8.0 are considered optimal for the maintenance of a healthy lake ecosystem.
The pH in the upper water of Great Sacandaga Lake at the Narrows ranged from 6.86 to 7.11 and at Sinclair Point ranged from 6.83 to 7.13. The pH of the bottom water at the Narrows ranged from 6.32 to 7.08. Based solely on pH, Great Sacandaga Lake's acidity levels should be considered satisfactory.
Alkalinity
Alkalinity (acid neutralizing capacity) is a measure of the buffering capacity of water, and in lake ecosystems refers to the ability of a lake to absorb or withstand acidic inputs. In the northeast, most lakes have low alkalinities, which mean they are sensitive to the effects of acidic precipitation. Typical summer concentrations of alkalinity in northeastern lakes are around 10 ppm.
The alkalinity of the upper water of Great Sacandaga Lake at the Narrows ranged from 17.2 ppm to 22.4 ppm and at Sinclair Point ranged from 17.2 ppm to 24.2 ppm. The alkalinity of the bottom waters at the Narrows ranged from 15.8 ppm to 20.6 ppm. These values indicate low sensitivity to acidification.
Calcium
Calcium is one of the buffering materials that occur naturally in the environment. However, it is often in short supply in Adirondack lakes and ponds, making these bodies of water susceptible to acidification by acid precipitation. Adirondack lakes containing less than 2.5 ppm of calcium are considered to be sensitive to acidification.
The calcium of the upper water of Great Sacandaga Lake at the Narrows ranged from 4.78 ppm to 5.46 ppm and at Sinclair Point ranged from 4.73 ppm to 5.89 ppm. The calcium of the bottom waters at the Narrows ranged from 4.43 ppm to 5.12 ppm. These values indicate low sensitivity to acidification.
Total Phosphorus
Phosphorus is one of the three essential nutrients for life, and in northeastern lakes, it is often the controlling, or limiting, nutrient in lake productivity. Total phosphorus is a measure of all forms of phosphorus, both organic and inorganic. Total phosphorus concentrations are directly related to the trophic status (water quality conditions) of a lake. Excessive amounts of phosphorus can lead to algae blooms and a loss of dissolved oxygen within the lake. Surface water (epilimnion) concentrations of total phosphorus less than 0.010 ppm are associated with oligotrophic (clean, clear water) conditions. Concentrations greater than 0.025 ppm are associated with eutrophic (nutrient-rich) conditions. Concentrations in between are associated with mesotrophic conditions.
The total phosphorus in the upper water of Great Sacandaga Lake at the Narrows ranged from 0.007 ppm to 0.017 ppm and at Sinclair Point ranged from 0.009 ppm to 0.023 ppm. This is indicative of mesotrophic conditions in the upper waters.
Chlorophyll-a
Chlorophyll-a is the green pigment in plants used for photosynthesis, and measuring it provides information on the amount of algae (microscopic plants) in lakes. Chlorophyll-a concentrations are also used to classify a lakes trophic status. Concentrations less than 2 ppb are associated with oligotrophic conditions and those greater than 8 ppb are associated with eutrophic conditions.
The chlorophyll-a concentrations in the upper water of Great Sacandaga Lake at the Narrows ranged from 1.88 ppb to 7.24 ppb and at Sinclair Point ranged from 2.08 ppb to 11.23 ppb. This is indicative of mesotrophic conditions. Although we should note that during the Sinclair Point field sampling session on September 16, 2007 we witnessed a very serious algae bloom in the surface waters of the lake. The lake water was a bright fluorescent green and the algae bloom was very obvious to this observer. This also was the sample that had a chlorophyll-a level of 11.23 ppb.
Secchi Disk Transparency
Transparency is a measure of water clarity in lakes and ponds. It is determined by lowering a 20 cm black and white disk (Secchi) into a lake to the depth where it is no longer visible from the surface. This depth is then recorded in meters. Since algae are the main determinant of water clarity in non-stained, low turbidity (suspended silt) lakes, transparency is also used as an indicator of the trophic status of a body of water. Secchi disk transparencies greater than 4.6 meters (15.1 feet) are associated with oligotrophic conditions, while values less than 2 meters (6.6 feet) are associated with eutrophic conditions (DEC & FOLA, 1990).
Secchi disk transparency in Great Sacandaga Lake at the Narrows ranged from 3.4 meters to 6.8 meters and at Sinclair Point ranged from 2.7 meters to 6.4 meters. These values are indicative of late oligotrophic conditions to early mesotrophic conditions. Again we should note that during the Sinclair Point field sampling session on September 16, 2007 we witnessed a very serious algae bloom in the surface waters of the lake. The lake water was a bright fluorescent green and the algae bloom was very obvious to this observer. This also was the day that we had a secchi disk transparency of 2.7 meters.
Chloride
Chloride is an anion that occurs naturally in surface waters, though typically in low concentrations. Background concentrations of chloride in Adirondack Lakes are usually less than 1 ppm. The primary sources of additional chloride in Adirondack lakes are road salt (from winter road de-icing) and wastewater (usually from faulty septic systems). The most salt impacted water in the Adirondacks usually has chloride concentrations of over 20 ppm.
The chloride of the upper water of Great Sacandaga Lake at the Narrows ranged from 7.6 ppm to 11.8 ppm and at Sinclair Point ranged from 6.9 ppm to 10.5 ppm. The chloride of the bottom waters at the Narrows ranged from 6.5 ppm to 10.2 ppm.
Conductivity
Conductivity is a measure of the ability of water to conduct electric current, and will increase as dissolved minerals build up within a body of water. As a result, conductivity is also an indirect measure of the number of ions in solution, mostly as inorganic substances. High conductivity values (greater than 50 mohms/cm) may be indicative of pollution by road salt runoff or faulty septic systems. Eutrophic lakes often have conductivities near 100 mohms/cm, but may not be characterized by pollution inputs. Clean, clear-water lakes in our region typically have conductivities up to 30 mohms/cm, but values less than 50 mohms/cm are considered normal.
The conductivity in the upper water of Great Sacandaga Lake at the Narrows ranged from 51.2 mohms/cm to 63.6 mohms/cm and at Sinclair Point ranged from 47.8 mohms/cm to 61.2 mohms/cm.
Dissolved Oxygen
The dissolved oxygen in a lake is an extremely important parameter to measure. If dissolved oxygen decreases as we approach the bottom of a lake we know that there is a great amount of bacterial decay that is going on. This usually means that there is an abundance of nutrients, like phosphorous that have collected on the lake bottom. Oligotrophic lakes tend to have the same amount of dissolved oxygen from the surface water to the lake bottom, thus showing very little bacterial decay. Eutrophic lakes tend to have so much decay that their bottom water will have very little dissolved oxygen. Cold-water fish need 6.0 ppm dissolved oxygen to thrive and reproduce. Warm water fish need 4.0-ppm oxygen.
The dissolved oxygen and temperature profiles for Great Sacandaga Lake for 2007 are presented in Appendix A. The dissolved oxygen stays fairly stable from the surface to the bottom in Great Sacandaga Lake until early August and September. During these months the oxygen level is insufficient and the water is too warm for cold-water fish survival but the water is okay for warm-water fish survival.
Summary and Conclusions
Great Sacandaga Lake was a moderately productive late oligotrophic to early mesotrophic lake during 2007. Based on the results of the 2007 sampling program, the acidity status of Great Sacandaga Lake is considered to have a low sensitivity to acidification. The pH values are satisfactory and the alkalinity values indicate low sensitivity to acidification.
It should be noted that the summer and early fall of 2007 were very dry and water levels were very low during the September and October sampling. These low water levels could have significantly affected the water chemistry and biology for Great Sacandaga Lake. These dry conditions and low water levels could have caused the very serious algae bloom in the surface waters of the lake that we witnessed on September 16, 2007 during the Sinclair Point field sampling session. The lake water was a bright fluorescent green and the algae bloom was very obvious to this observer. The secchi disk transparency was only 2.7 meters that day and the water sample had elevated chlorophyll-a level of 11.23 ppb and a total phosphorous concentration of 0.023 ppm.
Algae blooms, like the one that was witnessed on Great Sacandaga Lake during the September sampling, can have serious repercussions for any lake. Some species of algae, certain cyanobacteria, are toxic to humans, dogs and wildlife. Algae can cause water to taste different or give the water a characteristic smell. Algae can also alter water chemistry. One of the most serious effects of an algae bloom is after they die and sink to the bottom of the lake they add organic material to the sediment which is broken down by aerobic bacteria. These bacteria can use up or lower the oxygen levels in the lower levels of a lake. If enough material is present, on the lake bottom, the bacteria will deplete all the bottom oxygen and leave the lower levels of the lake anoxic.
A Great Sacandaga Lake Water Quality study was also performed during the early to mid 1990's. This study was very different than the study the Adirondack Watershed Institute performed in 2007. This earlier study used three different stations to collect water samples that were different then the ones used in 2007. The earlier study focused on fecal coliforms and heavy metals with only temperature, Secchi disk transparency, dissolved oxygen and pH performed in both the earlier study and the present study. The present study focused on existing water quality with special attention to nutrient levels and algae growth.
That being said, a comparison of the 1990's study to the 2007 study led to similar results. Both studies showed a very similar temperature profile. Both studies also showed a similar dissolved oxygen profile and loss of dissolved oxygen after 6 meters to the lake bottom. The 1990's study showed a lake with an average pH of 6.5. The 2007 study showed mark improvements with pH values ranging from 6.83 to 7.13. Finally, the 1990's study showed average Secchi disk transparencies of 2.7 meters in 1995 to 3.8 meters in 1992 and 1993. The earlier study notes the drop in Secchi disk transparency in 1995 but with no explanation. The Adirondack Watershed Institute 2007 study shows transparencies ranging from 2.7 to 6.8 meters. This does show overall average improvement in lake clarity but both 1995 and 2007 had a low transparency of 2.7 meters.
Appendix A
Water Quality Data
