Nutrient transient storage by the invertebrate assemblage in streams with contrasting nutrient loads

摘要

Headwater streams account for most of the channel length in lotic networks, are intimately connected with the terrestrial milieu and are biogeochemical hotspots (sensu McClain et al. 2003) at the landscape scale. These headwaters can influence larger downstream ecosystems such as rivers, estuaries and even coastal waters through longitudinal linkage of local biogeochemical processes (Alexander et al. 2000, Meyer & Wallace 2001). During the transit from uplands to oceans through lotic networks, nutrients undergo multiple cycles of uptake, biological, chemical and physical storage and remineralization -processes that can formally be described by the nutrient spiraling concept (Webster & Patten 1979, Newbold et al. 1981). While recent research on stream nutrient dynamics mostly focused on pristine ecosystems, little is known about human-altered streams. While we appreciate the role of periphytic algae in nutrient cycling (Mulholland 1996) and begin to understand the consequences of microbial biofilms for ecosystem processes (Battin et al. 2003a), relatively little is known about the immediate effects of invertebrates on whole-stream nutrient retention. The aim of this conceptual paper is to place benthic invertebrate consumers within the framework of stream nutrient dynamics in pristine and nutrient-enriched situations.