The influence of periphyton biomass and density on grazing in Physella virgata

Document Type


Publication Date



We studied how differences in periphyton colonization interval and snail density affected grazing rates in Physella virgata, and whether snails controlled periphyton biomass. Both egestion rates and incorporation rates of 14C labeled periphyton were estimated in laboratory experiments. Periphyton biomass increased with field colonization interval in all experiments, but did not consistently influence estimates of grazing rate. However, increased periphyton abundance in one of the experiments could still explain higher grazer rates in that year, although larger snail body size is a confounding explanation. Increased snail density also resulted in decreased grazing rates, as observed in earlier studies with this snail species, as well as in studies with other snail grazers. Our results suggest grazing rates and resulting impacts may change seasonally with variation in either periphyton biomass, grazer life-history stage or population density.

Publication Title


This document is currently not available here.