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Water Conditions - How's the Water

How’s the Water?
This is the thirteenth year since the grass carp have been introduced (October 1994) into Lake Mahopac for controlling the Eurasian Milfoil population, and the ninth year the Louis Calder Center performed both the water quality monitoring and vegetation study for Lake Mahopac.  The sampling was conducted on August 4, 2006 at the same sites of the previous years.  The report on this years sampling is expected shortly.
The grass carp are continuing to keep the Eurasion Milfoil from reestablishing itself at the annual sampling sites; however as in the previous year there have been sightings of milfoil in the lake by some residents.  This is the third year that another plant, Wild Celery, has also been seen in some of the coves around the lake.  This plant is a native (non-invasive) to Lake Mahopac and should not been considered a threat to the lake’s ecosystem.  Aquatic vegetation is a source of (1) food for fish and small insects, (2) protection for breeding fish and (3) oxygen.  A moderate population of aquatic plants (20 to 30%) is essential for the long-term health of the lake.
Water temperature was warmer and oxygen lower this year as compared to last year.  This is the second year that oxygen levels were lower.   Oxygen levels are affected by (1) temperature (warmer water equals less oxygen) or (2) consumption of oxygen by fish and bacteria is greater than production of oxygen by plants and algae.  Additionally, nitrogen levels were higher near the bottom of the lake where nutrient loading under low oxygen levels is greatest.
In summary, the grass carp are still keeping the Eurasion Milfoil from dominating in the lake and the water quality of Lake Mahopac is good.
More about Eurasion Milfoil: