Date of Award

Summer 2014

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Ocean & Earth Sciences

Committee Director

John R. Donat

Committee Director

Andrew S. Gordon

Committee Member

Kenneth Mopper

Abstract

This dissertation presents work focusing on copper and organic copper binding ligands in laboratory cultures and the Elizabeth River, Virginia. Laboratory cultures of the marine bacterium Vibrio parahaemolyticus were used to demonstrate the influence of elevated copper concentrations on copper-complexing ligand and thiol production. Copper-complexing ligands similar in binding strength to the strongest natural ligands were detected in V. parahaemolyticus cultures (log K′CuL = 11.8–13.2). A strong correlation (r2 = 0.973) was found between total thiol and copper-complexing ligand concentrations at all copper concentrations examined.

A yearlong seasonal study was undertaken in a heavily polluted estuary to ascertain seasonal variations and correlations between dissolved thiols, copper-complexing ligands, and total dissolved copper. Copper-complexing ligands and thiol compounds were found to vary seasonally and corresponded to seasonal changes in abundance of bacterioplankton, autotrophic picoplankton, and chlorophyll a, suggesting a biological source. Data indicate thiol compounds contribute to the ligand pool with conditional stability constants (log K′CuL) between 11.7–12.6.

A simple box model was developed for total copper in the Elizabeth River, Virginia using data from two estuarine transect cruises, the yearlong seasonal study, and limited point source information. The two estuarine transect cruises recorded total dissolved copper concentrations increasing up the Elizabeth River from 6.6 ± 1.0 nmol L−1 to 50.7 ± 0.9 nmol L−1. Results revealed a net statistically significant input of total dissolved copper to the river as a whole. This result suggests that an important copper uptake process has not been considered since no evidence indicates total dissolved copper concentration is increasing with time.

A series of in situ experiments in the Elizabeth River, Virginia revealed that an intact estuarine microbial community responded to copper stress by production of extracellular high-affinity copper-complexing ligands. The rate of ligand production was dependent on copper concentration and resulted in a reduction of the concentration of free cupric ions, Cu2+, by more than three orders of magnitude during a 2-week period in one experiment. This interactive response to copper stress may represent a feedback system through which microbial communities can potentially buffer dissolved Cu2+ ion concentrations, thereby regulating copper bioavailability and toxicity.

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DOI

10.25777/krh1-5b23

ISBN

978049607603

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