Date of Award

Spring 5-15-2016

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Marine Biology

Advisor

Mark Wells

Second Committee Member

Paul Rawson

Third Committee Member

Ian Bricknell

Abstract

Shellfish serve as first line sentinels to measure challenges to ecosystem health, including marine toxins, viruses and pathogenic bacteria. Many vibrios occur naturally in coastal estuaries generally at low abundances, but pathogenic vibrio species can become human health issues when they proliferate during warm periods. Depuration of these pathogens from bivalves varies as a function of bivalve pumping rates and bacterial growth rates. Projecting how climate change at higher latitudes may affect oyster and other bivalve aquaculture requires knowledge of how temperature influences the depuration rates of these species. Although this process is reasonably well understood for warmer water conditions, such as the Gulf of Mexico, there is far less information about pathogenic bacteria depuration rate under higher latitude, cold water conditions, such as the Gulf of Maine.

To understand the effects of temperature on depuration of the pathogenic vibrios in the Eastern oyster, Crassostrea virginica, Gmelin, 1791, the present study examined the depuration rates of pathogenic V. anguillarum in eastern oysters at different temperatures. The growth rates of V. anguillarum at different temperatures were measured as well. The collected data were used to generate the depuration timetable which can estimate the depuration times needed to render the contaminated oysters safe to consume.

The study shows that depuration time of the eastern oyster increase sharply as a function of temperature between 15-25°C, a difference attributable mainly to temperature effects on bacterial growth rates. The findings will help aquaculture growers reduce the off-market time due to vibrio contamination and provide a starting point for model other environmental effects on oyster depuration efficiencies. We suggest that alternate strategies for managing of shellfish aquaculture likely will be required in the future to adjust to the longer windows of warm periods, particularly in higher latitude, cold water regions.

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