Effects of episodic sedimentation on the net-spinning caddisflies Hydropsyche betteni and Ceratopsyche sparna (Trichoptera: Hydropsychidae)

Abstract

Net-spinning caddisflies commonly inhabit the chronically sedimented waters of midwestern agricultural catchments despite the presumed costs of sedimentation-induced gill-and net-fouling. We conducted a laboratory experiment to determine whether larval growth and survival of Hydropsyche betteni and Ceratopsyche sparna are affected by daily exposure to moderate levels of sedimentation. Sedimentation did not alter the relative growth rate of either species although slight losses by H. betteni and gains by C. sparna produced significant differences between species. H. betteni had a decreased likelihood of survival in sedimentation treatments relative to controls, but significantly outperformed C. sparna overall. Larval C. sparna are reportedly more sensitive than H. betteni to the instream effects of agricultural land use; however, the results of this experiment suggest that this differential sensitivity is probably not caused by episodic increases in suspended sediment concentration.