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Open Access Publications from the University of California

Organic Carbon in the Marine Enviornment: Redox State as a Measure of the Health of California Estuaries


Anthropogenic nutrient enrichments can have a significant effect on the redox state in estuarine systems. Increased nutrient `loading' leads to higher productivity and a subsequent increase in organic matter sedimentation. Respiration of this organic matter consumes dissolved oxygen, sometimes leading to hypoxic conditions in overlying water. Nutrients and toxins can then be released from the sediments to bottom waters, leading to catastrophic fish kills during overturn events.

My thesis work is focused on defining the relationship between organic carbon burial and redox state (relative progress of oxidation and reduction reactions) in sediments of estuarine systems in coastal California. Reduced species other than organic carbon are produced in sediments by organic carbon oxidation. This is important because alteration of the redox balance in estuarine sediments has a direct effect on dissolved oxygen concentrations of overlying waters, which have been identified by the National Estuary Program as one of the most important factors determining the health of estuarine ecosystems.

I will focus on characterizing the sedimentary redox conditions of two California estuaries using an automated Combustion Oxygen Demand Instrument (COxD): San Francisco Bay, a heavily impacted system, and Elkhorn Slough, a more pristine system. This work will contribute to understanding the importance of redox state in assessment and planning for the future of highly impacted estuaries such as the San Francisco Bay, and may help assess the success of restoration efforts of more pristine coastal wetland regions, such as Elkhorn Slough. Unique data produced as part of my thesis work will contribute to a new understanding of anthropogenic alteration of estuarine ecosystems and effects on coastal water and sediment quality. This work addresses the delicate balance of sustainable human progress and conservation of ecosystems vital to maintaining habitat and biodiversity in the California coastal zone.

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