BENTHIC MACROINVERTEBRATES OF AN IMPOUNDED PRAIRIE STREAM AS AFFECTEDBY COMPLETE IMPOUNDMENT DRAWDOWN

The benthic macroinvertebrates of Boomer Creek, Oklahoma, were surveye d in spring 1993, approximately four years after the complete drawdown of Boomer take, an impoundment of Boomer Creek. Drawdown restored the old stream channel within the lakebed to free-flowing conditions, whi ch resulted in a temporary reestablishment of Boomer Creek through the lakebed site. Collections of invertebrates were made at eight locatio ns in each of three stream reaches: upstream and downstream of the for mer impoundment, and in the stream channel within the former lakebed. Forty-three taxa were found in the stream, 33 of which occurred in the lakebed channel. Macroinvertebrate composition differed significantly among the three stream reaches, but macroinvertebrate densities did n ot. Dominant taxa in all areas were oligochaetes, chironomids. and a c orixid predator of these groups, Trichocorixa sp, Other common taxa fo und included Hyalella azteca, Procambarus sp., Physella sp., and Sphae rium sp. Thirteen taxa found in the lakebed channel were also found in an earlier (pre-draining) study of Boomer Lake macroinvertebrates.