Stream bed organic carbon and biotic integrity

Abstract

Allochthonous carbon is the basis of the detrital food web in low-order, warmwater stream ecosystems, and stream-bed sediments typically function as carbon reservoirs. Many of the same factors that govern carbon input and storage to streams (e.g. riparian vegetation, large wood, heterogeneous boundaries) have also been identified as key attributes of stream fish habitat. 2. Effects of channel incision on sand-bed stream carbon reservoirs and indices of biological integrity (IBIs) based on fish collections were examined for four streams exhibiting a range of incisement in northern Mississippi. Observed mean C concentrations (mass percentage) ranged from 0:24 � 0:36% for a non-incised stream to only 0:01 � 0:02% for a severely incised channel, and were not correlated with large wood (LW) density, perhaps because LW density at one site was elevated by a habitat rehabilitation project and at another site by accelerated inputs from incision-related riparian tree fall. Fish IBI was positively correlated with bed C (r ¼ 0:70; p ¼ 0:003), and IBIs for reference streams were more than 50% greater than those computed for the most severely degraded sites. 3. More testing is needed to determine the efficacy of stream bed C as an indicator, but its importance to warmwater stream ecosystems, and the importance of covarying physical and hydrologic conditions seems evident. Published in 2008 by John Wiley & Sons, Ltd.