COS 234-2 - Investigating links between host vital rates and severity of infection during interactions between Eastern oysters (Crassostrea virginica) and the pathogen, Perkinsus marinus

Abstract: The Eastern oyster, Crassostrea virginica, is a commercially important foundational species that provides crucial ecosystem services such as water filtration and habitat formation in estuarine systems. Eastern oysters are infected by Perkinsus marinus, a protozoan pathogen that has been associated with oyster mass mortalities in some regions. Although infection with P. marinus is known to impact oyster vital rates, how and at what point biological functions are lost as intensity of infection increases is unknown. In other words, we lack an understanding of how disease symptoms scale with infection intensity. We investigate how oyster feeding rate, growth rate, and body condition are depressed during progression of P. marinus infection, and what the consequences are for oyster survival. These foundational data will provide insight into how oyster ecosystem services may shift during P. marinus epidemics.

We collected wild-caught oysters from intertidal sites in Apalachicola bay. The oysters varied naturally in both infection status and infection intensity. A subset of oysters was assayed for feeding rates immediately following collection and were dissected to quantify disease parameters. This first assay allowed us to evaluate whether and how feeding rate was affected by infection presence and intensity. The remaining oysters were held in isolation under standard laboratory conditions for six weeks, during which a subset of oysters was sacrificed weekly to assess changes in infection intensity over time, and all other oysters were allowed to die naturally. Upon death (whether natural or experimental) all oysters were dissected for infection data and assessed for body size and condition. The results of this study will elucidate how disease can affect ecosystem function by altering feeding rates of important filter feeders and by altering habitat availability for other estuarine species.