The role of shredders in detrital dynamics of permanent and temporary streams

Abstract

The goals of this study were 1) to integrate several aspects of detrital dynamics with the composition and production of shredder populations and 2) to present evidence of a shredder regulatory role in headwater strewn detrital dynamics. The importance of leaf shredding aquatic insects (shredders) in the breakdown of leaf detritus and production of particulate organic matter (POM) was evaluated in three permanent and three temporary southern Appalachian headwater streams. Shredder population dynamics were compared to several stream detrital parameters: CPOM breakdown rates, POM concentrations, average POM particle sizes, and POM transport. In general, permanent streams with the greatest shredder densities, biomass, and annual production rates had the fastest leaf breakdown rates, highest low-flow POM concentrations, largest average POM particle sizes and greatest POM transport estimates.

Temporary stream environments depressed shredder populations resulting in a reduction of detrital processing and POM transport. Microbial activity, stream velocity, base-flow discharge, and water temperature did not correlate with detrital parameters for comparisons between permanent and temporary streams. Shredder contribution to total benthic CPOM breakdown in the six study streams ranged from 31% in a permanent stream to 1% in a temporary stream.