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Abstract

To more fully understand Ferguson Lake as an ecosystem and eventually relate its water quality and production potential to fisheries management, several limnological variables were sampled monthly from April 1997 through March 1999. Vertical profiles of temperature and dissolved oxygen were recorded, and water samples from 0.5 m. depth were tested for turbidity, pH, total alkalinity, total hardness, ortho-phosphate, nitrate-nitrogen, sulfate, iron and specific conductance. Evaporation rate experiments, spillway discharge and rainfall records were used to estimate lake hydrology. Depth transects on the lake and USGS topographic maps were used to measure and calculate morphometric and watershed features. The lake is essentially the deep end of a swamp (dmax =4.27 m.; dmean =1.92 m.) which is dominated by a lowland hardwood species-pine mix. Numerous cypress (Taxodium distichum) and tupelo gum (Nyssa aquatic) trees stand in the uppermost one-third of the lake. The rapid deposition and slow decomposition of organic debris on the lake bottom are the primary contributors to the brown water, relatively low pH, and hypoxia in and near the sediments from May through November. There was no evidence of thermal stratification, and pH ranged between 6 and 7, except for brief periods of rapid photosynthesis during the summers. Alkalinity, hardness and specific conductance were quite low, compared to most natural waters in this region. Phosphate, nitrate and sulfur were also comparatively low, and iron was low except after rainfall events which resulted in fairly heavy runoff.

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