The Benthic Macroinvertebrate Community Of The Greer's Ferry Reservoir Cold Tailwater, Little Red River, Arkansas

This study provides an evaluation of the benthic faunal characteristics of the cold tailwater of Greer's Ferry Reservoir on Little Red River. This Ozark stream is characterized by cold and non-turbid water, and periodic drastic vacillation of water level, the results of a deep water discharge for hydroelectric generation. For these reasons the benthic macroinvertebrate community is qualitatively limited. Pool and riffle habitats were sampled at six-week intervals at each of three stations established between 500 m-23 km below the dam. Most physicochemical characteristics measured were found not limiting, except water temperature and current velocity. Benthic organisms were limited to 59 taxa. Longitudinal zonation was characterized by an increase in diversity downstream with 15,32, and 41 taxa collected at Stations 1,2, and 3, respectively. Overall dominant organisms numerically were oligochaetes, chironomids and isopods. Oligochaetes composed 62-79% of pool organisms collected. Isopods dominated riffles with 37-81% of organisms collected. Chironomids were usually the second most ahundant in riftles and pools. The mean numerical ding crop was greatest at Station I with 1,241 organisms/m-2 and lowest at Station 2 with 437 organisms/ m-2.

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