Abby Popp

M.S., Limnology and Marine Sciences, 2005

Advisor: Emily Stanley

Abstract:   Longitudinal patterns of carbon, chlorophyll, and nutrients in the Wisconsin River
Small streams are efficient processors of nutrients relative to large rivers, which are assumed to transport nutrients downstream without substantial transformation or retention. However, recent studies have suggested that processing in large channels may be substantial. The goal of my research is to investigate longitudinal patterns of water chemistry in a 36-mile reach of the 7th-order Lower Wisconsin River to assess the degree of large-river nutrient processing. Parameters of interest include DOC, specific UV absorbance (SUVA; a measure of DOC quality), chlorophyll, nitrogen (N) and phosphorus (P). Longitudinal patterns vary seasonally and as a function of river flow, however downstream increases in chlorophyll, nitrate, dissolved phosphorus, and dissolved organic carbon loads are common. These spatial patterns indicate substantial loading of carbon along the length of the river (likely from floodplain wetlands), and provide evidence of significant in-channel carbon and nitrogen transformation in the Wisconsin River. Taken together, these trends indicate that large rivers have the potential to transform nutrients and alter the form and amount of nutrients exported from the basin.

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