Structural and Functional Organization of Macroarthropod Communities in a Mined Versus a Pristine Stream in the Cumberland Mountains of Eastern Tennessee

The effects of surface mining coal on the structural and functional organization of macroarthropod communities as a result of changes in the physical structure of small streams was investigated. Two first order streams in the Cumberland Mountains of eastern Tennessee, a pristine reference stream and a stream mined approximately 15 years earlier, were compared for particulate organic matter (POM) dynamics, structural and functional group composition, and productivity of their mecroarthropod communities. POM dynamics of the two streams were compared by measuring their input, standing stock, and processing in each stream. Macroinvertebrates were sampled with standard Surber samplers. The community structure of the two streams was compared in terms of taxonomic composition, abundance, species richness, and Shannon diversity. Functional group composition of the macroarthropod communities were compared using the functional group classification of Merritt and Cummins (1984). Productivity of the dominant taxa was calculated by the size-frequency method. The total productivity and productivity within functional feeding groups were then compared. Input and standing stock of POM in the two streams was similar. Faster rates of POM processing in the mined stream resulted from greater macroarthropod shredder densities. Differences in POM processing, macroarthropod functional group composition, and productivity within functional groups between the two streams suggest that their macroarthropod communities are functionally different. The lower abundance, species richness, and diversity were typical of the structural differences reported for other macroarthropod communities in mined streams of this region. Overall productivity of the surface mined stream was similar to the reference stream, although it was disturbed differently between functional groups. The results indicated that analysis of the functional group organization of mined streams reveals important differences in their ecology which could be underestimated or overlooked by conventional indices of community structure. Taxonomic surveys and diversity indices provide useful tools for monitoring and detection of environmental degradation. However, additional understanding of the causal relationships between environmental disturbance and biological change can be obtained from a functional approach which can identify its effects on specific biological processes in the stream community