Biogeographic Analysis of Eastern Oyster Microbial Associates in the Choptank River

Widmayer, Samuel
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University of Delaware
The eastern oyster (Crassostrea virginica) is a keystone member of the Chesapeake Bay ecosystem, performing critical ecosystem functions. Preservation of this species requires more comprehensive understanding of factors affecting health of populations. Diverse bacterial symbiotic associations with host organisms can provide benefits such as alternate nutrient acquisition and competitive exclusion of pathogens. This study sought to further characterize the eastern oyster extrapallial fluid microflora in a biogeographical context, and to determine if the structure of this community is subject to location specific influences or environmental variation. In June 2011 samples were collected at four oyster bars along the Choptank River near Cambridge, MD and 16S rRNA gene amplicon libraries were constructed with barcoded primers to facilitate multiplex sequencing on the Pacific Biosciences RS2 platform. A number of OTUs were uniquely enriched (Student T-Test; p < 0.05) in both oyster extrapallial fluid and the surrounding water column and at specific sample locations (Kruskall-Wallis; p < 0.05). Community structure in oyster extrapallial fluid was location-specific (ANOSIM; p = 0.019), yet location was not a significant influence in determining community differences in Choptank samples (Mantel Test; p > 0.05). A distance-decay relationship exists for community structure between populations separated by approximately 50 km in oyster extrapallial fluid to a far less extent than in water, indicating a degree of conservation of core community structure, subject to transient changes due to environmental variation.