Stream invertebrate community functional responses to deposited sediment

We investigated functional responses of benthic invertebrates to deposited sediment in four Missouri USA streams. In each stream, invertebrates were sampled along continuums of deposited sediment (particles <2 mm in size) from 0 to 100% surface cover in reaches of fairly homogeneous substrate composition, current velocity, and water depths. Correlations, graphical representations, and the cumulative response curves of feeding and habit groups provided strong empirical support for distinct community functional changes due to deposited sediment. Feeding groups were more sensitive to deposited sediment than habit groups. Densities of all the feeding groups decreased significantly with increasing deposited sediment, while relative densities of gatherers increased significantly. Taxa richness also decreased significantly for all the feeding groups except for the shredders. Increases in deposited sediment were related to significant density decreases for only the clingers and sprawlers in the habit group, resulting in significant increases in the relative densities of both burrowers and climbers. Clingers, sprawlers, and swimmers also showed significant decreases in taxa richness. ?? Eawag, 2005.