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An experimental manipulation to assess ecological impacts of riparian disturbances on small stream ecosystems.
Carroll, Denise1, Dibble, Eric1, Schoenholtz, Stephen1, 1
ABSTRACT- Small stream and riparian ecosystems have been the focus of numerous federal laws designed to maintain the integrity of water quality. Riparian disturbances can be an important factor affecting water quality and the ecology of the aquatic community. Before environmental standards are implemented, it is important to understand the ecological impacts that anthropogenic activities, i.e., timber harvesting have on stream communities. Our goal was to assess potential impacts these disturbances have on instream habitat and aquatic communities. We conducted an experiment using 9 perennial first- and second order streams located in north central Mississippi. Operational logging activities were controlled and used as experimental manipulations. Water quality, substrate, flow and bank characteristics, along with fish and macroinvertebrate populations were quantified before and after the experimental treatments. Differences between upstream and downstream sampling points were compared, and an analysis of variance was used to test for treatment effects relative to instream habitat, and macroinvertebrate and fish functional and trophic assemblages. A linear regression was used to identify relationships between water quality variables and (1) fish abundance, and species richness, (2) macroinvertebrate abundance, diversity and family richness, and (3) biotic indices. Treatment effects were observed, and to further identify mechanisms responsible for community impacts we compared data to a sediment-movement study concurrently conducted on the same nine streams.
KEY WORDS: riparian distrubance, instream habitat, aquatic communities, fishes and macroinvertebrates