Date of Award


Document Type

Campus Access Dissertation

Degree Name

Doctor of Philosophy (PhD)


Biology/Environmental Biology

First Advisor

Jennifer Bowen

Second Advisor

Jarrett Byrnes

Third Advisor

William Robinson


Global seafood production has grown steadily over the past 50 years, with more than 58 million people employed in capture fisheries and aquaculture worldwide. Seafood accounts for approximately 17% of the global population’s animal protein intake, and fish are among the most traded food commodities. The productivity of global fisheries is owed, in part, to the microorganisms that dominate oceanic systems. Microorganisms are the Earth’s most abundant life forms and constitute nearly half of all living biomass. They are responsible for a great deal of the oceans’ primary and secondary production and are the main drivers of Earth’s biogeochemical cycles. Given the importance of microorganisms to maintaining sustainable marine fisheries and aquaculture, I sought to: 1) understand the influence of different oyster farming practices on sediment microbial communities; 2) explain the interactions of bacteria in estuarine sediments, water columns, and oysters; and 3) characterize the bacterial communities associated with lobster shell disease. I examined the role of aquaculture in estuarine microbial communities and found that differences in oyster stocking density associated with different farming practices altered sediment microbial community structure. However, oyster farming did not increase either the number of beneficial denitrifying bacteria or the number of Vibrio, a bacterial genus containing species commonly associated with shellfish poisoning. I also compared estuarine sediments, water columns, and oyster tissues and found distinct bacterial communities in each sample type. Despite these differences, there was overlap in the core community members from different sample types. I also examined the bacteria responsible for lobster shell disease. Analysis of samples taken from diseased lobster shells revealed a distinct bacterial community at the site of disease, with significant reductions in bacterial diversity compared to clean shell. Samples 0.5 cm from the site of disease also had altered community composition even though there were no visual symptoms of disease, thus indicating that initiation of lobster shell disease may begin earlier than previously proposed. Taken together, these results further reveal the complex relationships between harvestable seafood products and the bacteria that dominate marine habitats. Understanding these relationships will become increasingly important as global reliance on seafood products grows.


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