Comparative Lake Study of Five Lakes in the Adirondack Region

Comparative Lake Study in the Adirondack Region

Introduction

This Comparative Lake Study deals with samples and observations taken during the Freshwater Ecology Class conducted by the Rensselaer Fresh Water Institute during the two week period of August 12th - August 26, 1995. The purpose of the study is to compare different local lakes, based on their algae, macrophyte, and zooplankton populations, and their physical and chemical characteristics. The local lakes from which data was compiled during this study are: Lake George, Trout Lake, Lake Champlain at South Bay and Crown Point, Lapland Pond, and Silver Lake. All of these lakes can be found in Adirondack Park.

This specific report focuses on the physical characteristics monitored during the study. These characteristics include: temperature and dissolved oxygen profiles, light meter and Secchi disk readings, and coliform and Biochemical Oxygen Demand on the different lakes. Knowledge of these measurements gives an indication of the health and other ecological parameters of the lakes.

Temperature:

The temperature profile in a lake will differ due to factors such as depth of the lake and season of the year. Temperature determines what types of life can inhabit the water, due in part to the fact that temperature determines oxygen concentration at saturation.

Dissolved Oxygen:

Oxygen is often a limiting factor in determining how much life a body of water can support; therefore dissolved oxygen readings can indicate the different types of life (aerobic, photosynthetic, anaerobic) that may inhabit a lake.

Light Meter / Secchi:

Light intensity, as measured by a light meter, can give an indication of the productivity of the lake, since water rich in biological matter such as phytoplankton tends to absorb light, appearing murky. Light profiles also dictate to what depth aquatic vegetation can grow, as algae and macrophytes need light from the sun to conduct photosynthesis. If a light meter is not available, one may use a Secchi disk reading (the depth to where the black and white quadrants of the disk are no longer discernible) to roughly determine the depth to which 5%of the surface light intensity penetrates the water. Both light meter and Secchi depth readings have been taken, and are compared.

Coliform:

Analysis of both total coliform and fecal coliform, and fecal streptococci have been performed on beach and open water samples from the lakes. While total coliform indicates the amount of both natural growing and fecal coliform strains, both fecal coliform and fecal streptococci grow primarily in the digestive tracts of warm_blooded mammals. Coliform analyses can therefore indicate the degree of possible contamination by human sewage, and possible presence of other pathogens, present in the water.

Biochemical Oxygen Demand:

Biochemical oxygen demand represents the degree to which the breakdown of organic matter in a water sample consumes oxygen. This organic matter can be due to a highly productive environment containing a high level of live material, or to contamination from sewage or other biodegradable waste. In water characterized by a lower B.O.D., less oxygen is consumed by decomposition and respiration processes.



Methods and Procedures:

Temperature: For each lake we compiled a temperature profile starting with the surface temperature and worked our way to the bottom. We used a probe which reported both temperature and DO. Keeping the meter set on temperature we lowered the probe by increments of one meter and recorded the given temperature.

Dissolved Oxygen(DO): Using the probe, as we did for temperature, a DO curve was also obtained for each of the five lakes. This time the meter was set for the DO channel and the probe was lowered once again in increments of one meter. When we took these measurements, the probe was shaken lightly at each depth. If the probe were kept stationary when taking DO readings, a measurement of zero would be recorded. The probe works by passing electrical current through the oxygen right around the probe and in doing so uses the oxygen up, therefore making it necessary to keep the probe moving for a correct reading.

Light Intensity: The light intensity of each lake was measured in two ways.
a. The first method we used to measure light intensity was an underwater photometer. Similar to our temperature and DO readings we recorded the light intensity at increments of one meter. This light probe worked off the principal of vertical illumination catching the sun's rays on a horizontal probe. In between each reading we recorded the intensity right below the waters surface so we could find the percent of light transmission at each depth. Checking the intensity of the light below the surface also helped us to compensate for clouds which might have covered the sun between readings thereby decreasing the surface intensity reading.

b. The second method we used to measure light intensity was the Secchi disk. Depending on how far we could see the disk down in the water was our Secchi disk depth. The Secchi disk depth is approximately equal to the depth at which 5% of the light entering the surface is transmitted. By lowering the disk slowly, we would find a range where the four quadrants on the Secchi disk were no longer distinguishable and bring it back up to where it was distinguishable once again. Then we would take an average of this range for our Secchi disk depth. Since this method should be used by itself only when no other equipment is available, we used it to compare the light probe with the 5% relationship.

Coliforms: In the five lakes which we compared, coliform testing was performed on both beach and open water samples. The three coliforms we tested for were fecal, fecal streptococci and total coliform counts. For the beach samples we tested for fecal and total coliform, while for the open water sample we tested for all three. The samples were taken at each lake in a 250ml autoclaved bottle. Back in the lab we took 10ml of the sample and mixed it with 50ml of sterile water and filtered it. The filter was then placed on prepared media plates. Duplicates were made for each type of plate. So for each lake we had at for the beach samples, two (blue) plates for fecal coliforms and two (pink) plates for total coliforms. For open water samples there were two fecal coliform plates, two total coliform plates, and two (purple) fecal streptococci plates. The fecal plates were incubated in a water bath for 24 hours. The total coliform plates were incubated in the low temperature oven as well but for 48 hours. The plates were counted for colonies when the incubation times were up.

BOD: Due to time constraints of the course only four of the six sites we sampled had BOD performed on them. The lakes sampled for BOD were Trout Lake, Lake George, South Bay, and Crown Point. Duplicates were taken at each of these sites in Winkler bottles making sure no air bubbles were trapped in the bottle. The eight bottles were stored at room,temperature for five days in the dark. On the fifth day the samples were titrated using the Winkler method. This entailed adding one manganous sulfate pillow and one alkaline iodide-azide reagent pillow to each bottle and inverting them twice allowing each to settle in between inversion. When settled a sulfamic acid pillow was added to each bottle, which was inverted and allowed to settle again. The final step was to take 200ml of sample and titrate it with 0.025N sodium thiosulfate using iodine to signal color change.



Discussion

The first characteristic we observed in our six lakes was temperature profile. In five of the six lakes, there are thermoclines. These thermoclines are affected by the depth profile of the lake and the morphology of the lake's water basin which can offer protection from the wind. In shallow, non-protected lakes, the wind has the capability to thoroughly mix the water, resulting in a smaller range in water temperature. Generally, deeper lakes and lakes that are more protected are partially mixed, due to the wind, causing stratification, resulting in the presence of a thermocline.

Another characteristic we observed during the study was light intensity profile. This is greatly influenced by the amount of nutrients in the lake. As we know, the nutrients are the base of the food chain in these aquatic ecosystems. More nutrients result in a greater concentration of phytoplankton in the water. Phytoplankton absorb light, resulting in decreased light intensity with descending depth. Therefore, water containing more phytoplankton will be murkier, with a higher value of nu, the light extinction coefficient.

Also a key factor in the characterization of lakes is the dissolved oxygen profile. Photosynthesis, which produces oxygen, is carried out by phytoplankton and macrophytes during daylight hours. Respiration, which consumes oxygen, is a constant ongoing process. In lakes that have a high nutrient level, and therefore a high phytoplankton concentration, the water tends to undergo a dissolved oxygen gradient. Oxygen levels peak in the thermocline, down to the depth where photosynthetic organisms have enough light to carry out photosynthesis, and water is cold enough to hold an increased amount of oxygen, before DO declines relative to lake productivity at deeper levels, where there is not enough light for photosynthesis to occur.

Lastly, we also measured BOD (Biological Oxygen Demand) and coliform at different sites. BOD is a measure of the oxygen demand used by the respiration and decomposition processes, and coliform, a bacteria often present in fecal material, can indicate the presence of other pathogenic bacteria. Both measures can often, but not always, be related to the amount of pollution entering a body of water.

Lapland Pond

This is a brown water pond, with a depth of 4.2 meters. Shallow and protected, Lapland has an established thermocline at approximately 3 meters. Nutrient levels in Lapland are high, with a phosphorus concentration of 28.6 ppb, the highest of all the lakes. One would therefore expect this lake to have the highest value of nu, due to a high concentration of phytoplankton; however this does not occur, as a lack of phytoplankton diversity is caused by highly eutrophic conditions, resulting in a smaller variety of light wavelengths being absorbed. Lapland has a nu value of 1.5 and a secchi depth of 2.7m. Coliform levels are moderate, with beach and open water samples both averaging approximately 25 colonies per 100ml. Due to the high eutrophic level of this lake, anaerobic conditions exist at its bottom. This lake is highly eutrophic, bordering on dystrophic.

Lake Champlain, South Bay:

This site, with a depth of 7.2m has no thermocline. It is an unprotected, windy area, allowing for thorough mixing of the water. The phosphorus level is 17.6 ppb, resulting in our higher value of nu, 2.2, and a secchi depth of 0.85. This moderately high phosphorus concentration yields a high amount of phytoplankton, while still allowing for species diversity. This is why the nu value for South Bay is higher than that of Lapland Pond, even though Lapland has higher levels of phosphorus. The DO profile for this lake shows a decrease of oxygen, to a level of approximately 3 ppm at the bottom. The DO at the bottom recorded, reads 1.7; we believe that this is an error, due to submersion of the DO probe into the sediment. This lake had very high coliform counts in both the beach and the open water samples. BOD measures at 1.53. This lake is highly eutrophic.

Lake Champlain, Crown Point:

This lake site is 8.5m deep. The area is more protected and not as windy as South Bay, allowing a thermocline to be established at 5-6pm. Phosphorous concentration is 13.3 ppb. The nu value is 0.6, with a secchi depth of 5m. The DO profile, similar to South Bay, ranges from 8.24 to 4.7 ppm. Coliform counts are extremely high on the beach due to a high level of agricultural animals in the area, and more moderate in the open water. BOD reads 0.74 ppm. This site is eutrophic.

Trout Lake:

This lake has a depth of 15.8m, and a thermocline from 5.5 to 7m. Total mixing is inhibited by the depth of the lake, causing stratification to occur. The phosphorus level is moderate,. at 2.3 ppb. Trout Lake has a nu value of 0.52, and a secchi depth of 6m. The fact that this lake is moderately productive, coupled with its depth, yields a DO gradient which peaks at 11.5 ppm before it reaches zero at the bottom, repeating anaerobic conditions. Coliform reads at moderate levels from the beach (open water samples were not taken). BOD measures 1.33 ppm. The moderate nutrient level together with the Nu value of this lake classifies it as mesotrophic (nu = 0.3) bordering on eutrophic (nu = 0.5 - 2).

Lake George:

This dimictic lake was sampled at a depth of 20m (although it reaches 60m at its deepest parts), with a thermocline at 10m. The phosphorus concentration is low, at 0.7 ppb. The nu value is 0.29, and the secchi depth is 7.0m. DO reads 8.4 at the lake surface, increases to 10 ppm within the thermocline, and then returns to approximately 8.6 ppm. Coliform reads moderately in the beach sample (again, an open water sample was not taken). BOD measures 1.53 ppm. Lake George can be classified as an oligotrophic lake.

Silver George:

This lake has a measure depth of 16m, with a deep thermocline at approximately 12m. A phosphorus concentration of 0 ppm, together with the effects of acid rain, promote extremely low productivity. Silver Lake has a nu value of .17, and a secchi depth of 13.1m. This lake exhibits a DO profile similar to that of Lake George, beginning at the surface at 8.6 ppm, peaking in the thermocline at 12.9 ppm at 12m, and ending at approximately 7 ppm. Again, we believe that the DO value at the bottom (2.1ppm) is incorrect , due to the immersion of the DO probe into the lake sediments. Total coliform in Silver Lake measured 35 colonies per 100 ml in the beach sample, with all other readings measuring 0. This is due to the fact that, although beavers heavily populate the area, the water is very acidic and not conducive to the survival of coliform bacteria. Silver Lake can be classified as ultra-oligotrophic. This would be classified as an acid lake.


Graphs and Results

 Coliform Results
Phosphorus Results
Lake Depth Results


Related Topics

 Zebra Mussels


Adirondack Information

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