Open Access Kent State (OAKS)

Bacterial distributions among biofilms and the water column may be altered by a variety of abiotic and biotic factors including feeding and physical activities of macroinvertebrates. The purpose of this study was to examine the effect of macroinvertebrates on abundances and distributions of three species of bacteria that differ in their surface properties and niches. Eight invertebrate genera were examined; functional feeding groups included predators, shredders, filter feeders, and collectorgatherers. The three bacterial species responded to the presence of the macroinvertebrates in generally similar ways, although the species with the most developed ability to attach to surfaces (Burkholderia cepacia) apparently resisted dislodgment by macroinvertebrates. Bacillus thuringiensis, a relatively species-specific insecticidal bacterium, achieved higher abundances on invertebrate exteriors than did B. cepacia and Pseudomonas fluorescens. Orconectes reduced abundances of introduced bacteria on leaves and shifted distributions; a greater percentage of the bacterial populations was found in the sediments of the Orconectes microcosms than in microcosms lacking macroinvertebrates. These alterations were probably the result of consumption of bacteria from epiphytic biofilms and subsequent deposition in feces. Corbicula shifted distributions of two of the bacterial species so that a greater percentage of the populations was in the water column, perhaps as the result of burrowing activity. Both of these invertebrate species are common stream residents and may affect the distribution and persistence of natural and introduced bacteria.