Dam Bugs and Beyond: Influences of Dams on Downstream Aquatic Macroinvertebrate Community Structure and Associated Physiochemical Variables

In the context of the serial discontinuity concept, we investigated influences dams have on structuring physicochemical variables and aquatic macroinvertebrate communities along the stream continuum.  Seven streams were sampled (one in each of MD, OH, and WV and four in PA) a total of 5,100 m at predetermined distances below dammed sites. We tested the prediction that biotic richness and diversity (Shannon Index) would increase as distance from dams increased.  Furthermore, we hypothesized that dams would influence water quality and habitat variables, which would aid in explaining the structure of biotic communities along the stream continuum.  Multivariate methods (PCA and NMDS) were used to summarize and interpret gradients in physicochemcial and biotic data respectively.  We suggest that dams may impact physicochemical variables and thus biota in a longitudinal fashion that is congruent with the serial discontinuity concept.  Results will be discussed.