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Abstract

One hundred thirty benthic samples were collected on 33 visits to Ferguson Lake, Saline County, Arkansas, between May 1997 and October 2000. Sediments were visually examined and described, and some were returned to the lab for sediment oxygen demand (SOD) analysis. Fourteen taxa, representing five phyla of invertebrates, were identified. In all samples, oligochaetes, chaoborids, and chironomids comprised the majority of individuals, reaching densities up to 7449, 14,208, and 8783 per m2, respectively. When seasonally grouped, largest total abundances and greatest abundances of most taxa were collected during the winter months (December-February). A minor abundance peak occurred in July due to a mid-year generation of Chaoborus. Some significant differences in abundance between seasons were present. The number of taxa collected per sample was also highest in winter but not significantly different from other seasons. Community diversity indicators were lowest in summer. Sediments over most of the lake consisted of a variable thickness (1 to 4 cm) layer of woody detritus above a deeper, rich, thinly divided mix of organic muck and inorganic particulates. Too little variation in sediments existed to test for macrobenthos preferences. The SOD tests revealed a nearly complete oxygen depletion in the chamber in 24 hours.

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