Prevalence, distribution and environmental factors associated with Perkinsus marinus infections in eastern oyster, Crassostrea virginica, in Apalachicola Bay, Florida, USA

Master's thesis in Environmental technologyPerkinsus marinus is a protozoan parasite causing Dermo disease in the Eastern Oyster, Crassostrea virginica. The parasite spreads from oyster to oyster through the water column, and can cause extensive oyster mortalities, especially after periods with high temperature and salinity. This study investigated the distribution and weighted prevalence (prevalence and infection intensity) of P. marinus in C. virginica in Apalachicola Bay (Franklin County, Florida, USA), as a part of a larger project that investigates the decline of oyster populations and fishery collapse in the bay. The relationship between oyster health and P. marinus infections were also investigated. No differences were found in weighted prevalence of P. marinus infections in oysters within oyster bars, between oyster bars, nor between November 2012 and February 2013 sampling time points. Mean weighted prevalence of P. marinus infections in Apalachicola Bay was 1.01 ± 0.11 and 0.90 ± 0.05 (mean ± SE) for November 2012 and February 2013, respectfully. A negative relationship between oyster meat condition and P. marinus infection intensity was found. No other relationships were found between different internal and external oyster health condition indices and P. marinus infection intensity. Results from this study compared with other studies suggest that weighted prevalence of P. marinus in Apalachicola Bay oysters has increased since 2005. Drought periods in the Apalachicola River watershed are associated with reduced freshwater flow into Apalachicola Bay and elevated salinity, fostering conditions favorable for P. marinus infection in oysters.2015-06-1