The Glen Lake Association is a member of the Cooperative Lakes Monitoring Program (CLMP) which is a volunteer inland lakes water quality monitoring program. Every week during the summer volunteers measure water clarity (secchi disk visibility depth) and at various specified dates sample for phosphorus and Chlorophyll. We measure and sample on Big and Little Glen, Brooks, and Big Fisher lakes.
The CLMP website has data on Big Glen data going back to 1979 for secchi depths and to 2001 for chlorophyll and phosphorus. Water clarity has been improving on Big and Little Glen giving it that look of the blue Mediterranean. You might think this is a good thing, but maybe not Clarity is affected by suspended solids and algae. We believe clarity is increasing due to the removal of zooplankton and algae by zebra or quagga mussels. This means less food for small fish and greater depth where aquatic plants can grow. Our lakes have a lot of mussels. When we do our yearly invasive aquatic plant survey, we often bring up small mussels attached to the plants.
The following chart shows the numbers.
Phosphorus levels for Big Glen are averaging about 4 parts per billion over the last 18 years, dropping slightly. This is very good, indicating that we don’t have a lot of fertilizer or septic runoff into the lake. Some phosphorus is essential for plant and algae growth which is food for fish. Our level is very low.
Chlorophyll is the pigment that allows plants (including algae) to use sunlight to convert simple molecules into organic compounds via the process of photosynthesis. Measuring chlorophyll concentrations in water is a surrogate for actually measuring algae biomass.
The chlorophyll has been steady at less than 1 part per billion for 18 years. These are very low levels which indicates little fertilizer and septic runoff.
In some lakes, as septic systems get older and homes are upsized and lived in for more of the year, phosphorus and chlorophyll levels ramp up. This has not happened to Big Glen. The same is true for Little Glen, Brooks and Big Fisher lakes.