Ecosystem Functioning and Community Structure as Indicators for Assessing Environmental Impacts: Leaf Processing and Macroinvertebrates in Atlantic Forest Streams

Abstract

AbstractPrograms for evaluating environmental impacts are often carried out with chemical analyses that are inadequate for evaluating ecological aspects of rivers. In recent times there has been a strong movement towards biomonitoring using indices based on the structure of communities of organisms. Less attention has been given to functional parameters (ecosystem level processes such as decomposition, primary production, nutrient cycling, etc.), despite recent work that demonstrates their applicability. The breakdown of leaf material in streams provides a system in which an aspect of ecosystem functioning (decomposition) can be measured along with the community structure of the fauna associated with the leaves.We measured rate of leaf processing and the associated macroinvertebrates in 9 streams in 3 categories of environmental impact: Reference (pristine forest), Intermediate (pasture land‐use with intact riparian vegetation) and Impacted (pasture land‐use with degraded banks and stream‐bed). Leaf processing was fastest in the least impacted, “Reference”, streams. The abundance and taxon diversity of the associated fauna were not different among categories of impact. Thus this aspect of ecosystem functioning was more sensitive to perturbation than was the structure of the community in this case. We suggest that leaf processing can be a cheap and indicative parameter for biological assessment and monitoring. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)