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SFS Annual Meeting

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It is well documented that urbanization contributes a suite of physical, chemical, and thermal stressors to receiving waterbodies. We examined 67 chemical, physical and biological attributes of streams draining 49 randomly-selected watersheds in the metropolitan area surrounding Raleigh. Watersheds ranged in development impacts, with 0 to 99.7 % of their area in impervious surfaces. In contrast to prior studies, we found no consistent changes in habitat structure, channel dimensions or bed sediment size distributions along the urbanization gradient. We found that watershed urbanization did lead to large and consistent changes in receiving stream chemistry (with increases in NO3, bioavailable and algal-derived DOC and the trace metals Pb, Cd and Zn) and thermal regimes. These chemical and thermal changes were associated with declines in macroinvertebrate taxa richness and altered macroinvertebrate community composition, but were not associated with any consistent shifts in microbial community structure or taxa richness or with shifts in microbially-mediated biogeochemical processes (C mineralization, denitrification potential, substrate-induced respiration). Random reach selection in our region does not support the classic urban stream syndrome paradigm.

Brooke Hassett (Primary Presenter/Author), Duke University,;

Emily Bernhardt ( Co-Presenter/Co-Author), Duke University,;