Author

Kelly McCabe

Date of Award

Spring 2020

Document Type

Open Access Thesis

Department

Marine Science

First Advisor

Claudia Benitez-Nelson

Abstract

Excessive organic matter (OM) is driving declining dissolved oxygen (DO) concentrations in coastal ecosystems, worldwide. The quantity, source, and composition of OM transported to coastal ecosystems via stormwater runoff has been altered by land use changes associated with urbanization and subsequent headwater alterations that accompany urban stormwater management. To understand the role of stormwater runoff in the decline of coastal DO, biochemical oxygen demand (BOD) was determined for samples collected during rain events from the outfalls of a variety of stormwater infrastructure with watersheds spanning a range of development. Measurements of particulate and dissolved carbon and nitrogen and chlorophyll-a concentrations as well as stable carbon isotope (δ13C) values helped explain the drivers of stormwater BOD concentrations. Results suggest stormwater runoff is a significant source of labile OM to receiving waters, however BOD concentrations vary greatly both among and within sites in response to rain events. This variability in BOD was best predicted by concentrations of particulate OM (POM), especially chlorophyll-a concentrations, rather than the larger dissolved fraction of OM. These findings stress the importance of managing episodic stormwater pollutant discharge, especially POM, from urbanized areas to mitigate DO impairment in larger downstream systems.

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