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 carbofuran and its effects on aquatic macroinvertebrates in alkaline, Canadian prairie parkland ponds. Four ponds were sprayed with carbofuran in late July; four other ponds served as controls. Sixteen hours after spraying, concentrations of carbofuran in the water column ranged from 9-32 μg l(-1). After 124 h, concentrations had declined to 3-12μg l(-1). Carbofuran partitioned into submersed aquatic plants, ranging from three to 46 times greater in the plants than in the surrounding water. Carbofuran was below detection limits in most sediment samples. Among the aquatic macroinvertebrates considered in this study, the crustacean Hyalella azteca and trichopteran larvae declined significantly in abundance following the application of carbofuran. Coenagrionidae and small chironomid larvae did not decline following carbofuran application. Hyalella azteca abundance remained relatively low in treatment ponds through to May 1987, while trichopteran larval abundance had recovered by August 1986. There were no readily apparent shifts in community structure in this study, although slight, disproportionate increases 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.