Influence of Detritus upon Colonization of Stream Invertebrates

Abstract

The effect of introduced detritus on the colonization of cages by benthic invertebrates within the substrate of two stony streams was examined. Pairs of substrate-filled screen cages were buried to a depth of 10–20 cm within the substrate of Otter Creek, Sauk County, Wisconsin, and the East River, Gunnison County, Colorado. Variously conditioned coarse particular detritus was added to experimental cages, and no detritus to control cages. Total macroinvertebrates and total detritivores did not preferentially colonize cages enriched with detritus. Shredders showed higher colonization of experimental cages during fall trials using leaves conditioned by inoculation with microbial flora from Otter Creek. This observation reflects habitat choice by availability of high-quality food for shredders during the season of their greatest abundance. Shredders preferentially colonized detritus-enriched cages during combined summer trials in the East River and during summer trials when leaves were not microbially conditioned before use. Shredders in this high-altitude stream showed opportunistic colonization of introduced large-particle detritus where natural allochthonous matter was less readily available.Key words: detritus, streams, macrobenthos colonization, leaf conditioning, shredders, experimental manipulation