Relative Role Of Habitat Alteration And Heavy Metal Pollution In Degrading Southeastern Streams (presentation)

SNODGRASS, JOEL W., Charles Jagoe and J. Burger

We compared fish assemblages and habitat structure, and sediment and tissue levels of metals between a stream with urbanized headwaters and several control streams (with no development in their headwaters). Our goal was to evaluate the relative impacts of habitat alteration and pollution resulting from headwater urbanization, on downstream reaches. We documented fish assemblage and habitat structure in six, 100 m reaches in both impacted and control streams. Fish assemblage structure in the impacted stream was different from that in control streams; mean species richness and fish density in the impacted stream (7 species and 95 fish per 100 m of stream) were < half that observed in control streams (17 species and 407 fish per 100 m of stream). Habitat structure in the stream with urbanized headwaters also differed from control streams, with the urbanized stream having higher current velocities, fewer and shallower pools, less undercut bank and woody debris, and overall, less habitat variation. With the exception of lead and cadmium tissue levels, mean tissue and sediment levels of metals (Hg, Al, Cr, Mn, Ni, Cu, Zn, Cd, and Pb) were higher or similar in the control streams when compared to levels from the impacted stream. Lead and cadmium tissue levels were higher in the impacted stream, but these levels were well below tissue levels reported to be associated with adverse effects of these metals on fish. We conclude that habitat alteration due to headwater urbanization poses a greater risk than metal pollution to downstream reaches of southeastern streams.