Factors Affecting Dermo Disease (Perkinsus marinus) in Eastern Oysters (Crassostrea virginica) in Galveston Bay, Texas

The oyster disease Dermo (Perkinsus marinus) affects the viability of oyster reefs of Galveston Bay, Texas. Documenting the relationships between distribution and prevalence of Dermo disease in the eastern oyster (Crassostrea virginica) and environmental conditions is beneficial to management of the eastern oyster in Galveston Bay. We sampled four sites located in Galveston Bay every other month from November 2014 through September 2015. The focus of the study was the relationship of water quality parameters (i.e., fresh-water flow, salinity, water temperature, and water turbidity) to prevalence and parasite concentration of Dermo disease in oysters. Dermo was present in oysters at all reefs sampled, and Dermo prevalence was greatest at April Fool and Confederate reefs, but declined after heavy rainfall. Linear regression analysis indicated water variables such as temperature, salinity, turbidity, and fresh water inflow explained different amounts of the variability in the Mackin Dermo Intensity Scale among sampled reefs. We found combinations of low fresh-water inflow, high salinity, and high temperatures accounted for majority of the variance of Dermo in oysters located in Galveston Bay.