Chemical Barriers and Deflation of Fish Metacommunities in Mined Riverscapes

Localized impacts to streams can produce a mosaic of habitat conditions and fragment stream fish communities within riverscapes.  Although the effects of local conditions on fishes is well studied, deflationary consequences at the scale of riverscapes remain poorly understood.  We present results of a research program designed to quantify the cumulative effects of mining on fish assemblages within central Appalachian watersheds.  Our approach consists of: 1- constructing models to predict physico-chemical conditions continuously at the whole watershed scale; 2- testing alternative models of fish metacommunity structure; and 3- quantifying fish assemblage deflation at the riverscape scale.  Our results indicate that both local and regional processes influence fish assemblages simultaneously and that the relative importance of local vs. neighborhood controls varies among species.  We also show that localized impacts disrupt source-sink dynamics in fish populations, which in turn deflates fish biodiversity at the watershed scale.  We discuss the implications of these results as it relates to watershed restoration and conservation of aquatic biodiversity.