FATE OF CARBOFURAN AND ITS EFFECTS ON AQUATIC MACROINVERTEBRATES IN CANADIAN PRAIRIE PARKLAND PONDS

A multipond study was conducted in 1986 to determine the fate of carbo furan and its effects on aquatic macroinvertebrates in alkaline, Canad ian prairie parkland ponds. Four ponds were sprayed with carbofuran in late July; four other ponds served as controls. Sixteen hours after s praying, concentrations of carbofuran in the water column ranged from 9-32 mu g(-1). After 124 h, concentrations had declined to 3-12 mu g l (-1). Carbofuran partitioned into submersed aquatic plants, ranging fr om three to 46 times greater in the plants than in the surrounding wat er. Carbofuran was below detection limits in most sediment samples. Am ong the aquatic macroinvertebrates considered in this study, the crust acean Hyalella azteca and trichopteran larvae declined significantly i n abundance following the application of carbofuran. Coenagrionidae an d small chironomid larvae did not decline following carbofuran applica tion. Hyalella azteca abundance remained relatively low in treatment p onds through to May 1987, while trichopteran larval abundance had reco vered by August 1986. There were no readily apparent shifts in communi ty structure in this study, although slight, disproportionate increase s in Chironominae and Coenagrionidae in the treatment ponds following spraying may have resulted from such factors as reduced competition or a change in the size or composition of the food base.