Primary productivity and water quality were studied in Doe Valley Lake, a 147-hectare impoundment on Doe Run, a spring-fed stream in Meade County, Kentucky, from 13 June 1969 to 31 July 1972. Doe Valley Lake is monomictic during most winter seasons, but it is dimictic during more severe winters because of its morphometry and location on the borderline climatic region for dimictic lakes (37° N latitude). Oxygen depletion in the hypolimnion is severe, and anaerobic conditions usually prevail by late June. A hypolimnetic areal deficit of 0.038 mg/cm2/day was calculated. Supersaturation of oxygen in the epilimnion was common, and metalimnetic maxima exceeded 150 percent saturation in spring and early summer.
Primary productivity ranged from 44 to 1,192 mgC/m2/day and annual rates at Stations I and III were 277 and 255 gC/m2/yr, respectively. Productivity fluctuated considerably at Station I as a result of turbidity, but average daily rates and chlorophyll levels were higher than at Station III. Periodic flooding drastically lowered productivity and phytoplankton standing crops. Negative or low correlations were found between productivity and turbidity, pH, alkalinity, nitrates, and phosphates. The relationship between productivity and standing crop of phytoplankton varied throughout the year but positive correlations were observed on an annual basis. Chlorophyll a levels correlated fairly well with net phytoplankton. Except during summer, nannoplankton contributed more than 50 percent of the total carbon assimilation.
The inflowing stream, Doe Run, contributes valuable quantities of nutrients including carbon, nitrogen, phosphorus, and sulfur that enhance the productivity of the lake. Degradation of allochthonous leaf materials introduces significant amounts of carbohydrates, proteins, and lipids into the lake ecosystem, but inflow patterns characteristic of a spring-fed stream greatly influence the fate and availability of these nutrients.
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The work on which this report is based was supported in part by funds provided by the Office of Water Resources Research, United States Department of the Interior, as authorized under the Water Resources Act of 1964.
Bacon, Edmond J. and Neff, Stuart E., "Seasonal Changes in Water Quality and Primary Productivity in Doe Valley Lake" (1974). KWRRI Research Reports. 124.