Water quality data at 12 sites within an urban, a suburban, and a rural stream were collected contemporaneously during four wet and eight dry periods. The urban stream yielded the highest biochemical oxygen demand (BOD), orthophosphate, total suspended sediment (TSS), and surfactant concentrations, while the most rural stream yielded the highest total organic carbon concentrations. Percent watershed development and percent impervious surface coverage were strongly correlated with BOD (biochemical oxygen demand), orthophosphate, and surfactant concentrations but negatively with total organic carbon. Excessive fecal coliform abundance most frequently occurred in the most urbanized catchments. Fecal coliform bacteria, TSS, turbidity, orthophosphate, total phosphorus, and BOD were significantly higher during rain events compared to nonrain periods. Total rainfall preceding sampling was positively correlated with turbidity, TSS, BOD, total phosphorus, and fecal coliform bacteria concentrations. Turbidity and TSS were positively correlated with phosphorus, fecal coliform bacteria, BOD, and chlorophyll a, which argues for better sedimentation controls under all landscape types.

We investigated physical, chemical, and biological variables contributing to biochemical oxygen demand (BOD) in 17 North Carolina lotic and lentic water bodies affected by mild to severe hypoxia. Phytoplankton production created the dominant reservoir of labile carbon driving BOD, and subsequent hypoxia, in a Piedmont river subject to algal blooms, three urban streams, a set of anthropogenically affected tidal creeks, and two urban lakes. Autotrophic phytoplankton production contributed to the BOD load in some rural streams. Autochthonous heterotrophic processes, stimulated primarily by phosphorus and secondarily by nitrogen loading, were the major influences on BOD in two large black water rivers and some rural black water streams. Inputs of biochemical oxygen-demanding materials from storm water runoff contribute to BOD in some urban and rural streams and black water rivers. We suggest that reductions of hypoxia can be better achieved by a system-specific approach based on an array of factors that potentially influence BOD, including both autochthonous and allochthonous variables. In some circumstances targeting the nutrient(s) stimulating phytoplankton blooms will suffice to reduce hypoxia, but in other situations targeting nutrient(s) limiting bacterial production will be necessary. Reduction of non-point source inputs of biochemical oxygen-demanding materials derived from urbanization or other land disrupting activities will be critical in some cases.

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