Perkinsus marinus is a protistan parasite that infects the eastern oyster Crassostrea virginica and causes dermo disease. Since it was first identified, it has caused large-scale mortalities of oysters along the gulf and east coasts of North America. P. marinus prevalence, intensity, and resulting oyster mortality increase with temperature and salinity. Outbreaks occur during summer and fall, when water is warmest and salinity highest. Given the impacts of temperature and salinity on P. marinus-C. virginica interactions, we expect climate change to further affect this system, with potentially strong impacts in colder locations. Previous models of the P. marinus-C. virginica system are of two general types: proliferation-based models focused on tracking P. marinus abundance or disease transmission models focused on tracking susceptible and infected C. virginica individuals. Proliferation-based models show that including temperature and salinity dependencies leads to more realistic model predictions of within-host parasite abundance. As a whole, these models focused on large-scale dynamics rather than on the interactions between an individual host and parasite. Here, we present a simple model tracking the population dynamics of P. marinus in the local water volume and within their oyster hosts (Figure 1). We use existing time series data to derive responses for key parameters (filtration, parasite growth rate) to temperature and salinity. We then use the existing model to predict future dynamics under climate change.