Benthic macroinvertebrates of a southern Appalachian wild and scenic river
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Many stream-dwelling aquatic macroinvertebrates are functionally adapted to utilize resources associated with the bottom of channels. Local stream bed sediments are important components of macroinvertebrate habitat. Distribution of macroinvertebrate fauna within stream benthos is highly influenced by this factor. This study was undertaken to: (a) examine the effects of fine sediments on benthic macroinvertebrate assemblage structure within streams of a southern Appalachian watershed; (b) gain insight into ecological function within these streams; and, (c) examine benthic macroinvertebrate community structure along a longitudinal continuum within the same watershed. Results from this study indicate that fine, deposited sediments (” 2mm) covering stream beds are affecting benthic macroinvertebrate communities at both the mesohabitat and reach scale within headwaters of the Chattooga River watershed. Sensitive invertebrate taxa (Ephemeroptera, Plecoptera, Trichoptera taxa) declined within study reaches with elevated sediments. Shredder abundance was significantly reduced within reaches where levels of fine sediments were higher, and fine sediments influenced the composition of shredder assemblages. Large-bodied cranefly larvae were more predominant in channels containing higher amounts of deposited sediments and they replaced stonefly shredders. Fine, deposited sediments prevented some taxa from exploiting coarse leaf litter. There was also evidence indicating that fine sediments could be having a negative impact on algal resources in these streams. Fine sediments had differential effects on the sampled habitats: (1) in cobble riffles, the number of EPT taxa declined with increased fine sediments; (2) in bedrock outcrops, total assemblage abundances and grazer abundances were negatively correlated to reach-scale amounts of fine, deposited sediments; and (3) in depositional habitats, the second most frequently collected taxon (specific taxon varied with stream channel) was positively correlated to levels of fine, deposited sediments. Macroinvertebrate communities along a continuum of the Chattooga River watershed followed some, but not all river continuum concept predictions. Local habitat conditions influenced the composition of reach-level benthic macroinvertebrate communities. Invertebrate communities occurring in geomorphically distinct habitats (riffles, bedrock outcrops, and depositional areas) had unique structural patterns.