Invertebrate drift,discharge, and sediment relations in a southern Appalachian headwater stream

Drifting invertebrates and suspended sediments were collected at monthly intervals from June 1977 to May 1978. The numbers and biomass of drifting organisms reflected the seasonal cycles of aquatic insects. Some aquatic organisms showed behavioral drift either during a sample day or during some portion of their life cycle. Parapsyche cardis Ross and Diplectrona modesta Banks (Trichoptera: Hydropsychidae) dispersed as first instar larvae; few later instars of these two net-spinning caddisflies drifted. The drift of nymphal Peltoperla maria Needham et Smith (Plecoptera: Peltoperlidae) was apparently related more to detritus transport than to benthic densities or discharge alone. Power law relations between the magnitude of daily invertebrate drift and discharge or sediment variables are demonstrated for some taxa in Hugh White Creek. The general level of stream invertebrate drift appears to be related to detritus transport, and drift during storms is also related to detritus transport. During storms, terrestrial invertebrate drift was related to rainfall intensity, canopy washing, and channel expansion. Drift density of aquatic invertebrates in Hugh White Creek was within the range of previously reported values for other streams, but the estimate of yearly export (aquatic invertebrates = 134 g · y^?1; terrestrial invertebrates = 23 g · y^?1) is lower reflecting the smaller size of Hugh White Creek in comparison with those other streams.