Predicting the effects of hypoxia on oyster (Crassostrea virginica) growth and reproduction through the Dynamic Energy Budget model Ecological Modelling

Hypoxia in the world's oceans poses an increasing threat to marine organisms and ecosystems, and there is a need to scale individual effects in order to make predictions about the broader ecological consequences of reduced oxygen availability. Mechanistic models, such as the Dynamic Energy Budget (DEB) model, provide a useful framework for quantifying the effects of changing environmental conditions, such as hypoxia, on individual organismal response. While the standard DEB model is forced solely by temperature and food availability, recent additions to the model for some marine species have allowed for the modulation of DEB energy fluxes in response to oxygen availability. The eastern oyster, Crassostrea virginica, is a sessile marine invertebrate inhabiting coastal environments experiencing variability in oxygen availability for which a DEB model has already been parameterized, but dissolved oxygen has not yet been incorporated as a forcing variable. The present study uses observed oyster growth data from sites throughout the Chesapeake Bay experiencing a range of oxygen regimes to validate a DEB model for C. virginica, implementing a constraint on energy fluxes due to oxygen availability. The effect of dissolved oxygen is parameterized into the C. virginica DEB model using an oxygen correction factor to constrain assimilation, mobilization, and ingestion rates within the energy budget. The resulting model accurately predicts empirically measured oyster growth data, with an average deviation between simulated and observed shell lengths of 4.70 % across all sites assessed. The model is then used to make predictions about hypoxia's influence on growth and reproduction over the oyster's growing season using data from two additional sites in the Chesapeake Bay. Model outputs indicate that low oxygen exposure results in reduced growth for oysters, in both shell length (6.9 % reduction) and tissue mass (23.6 % reduction), as well as reductions in oyster fecundity (54.4 % reduction in number of eggs spawned) and alterations to spawning frequency during the summer, which collectively has the potential to negatively affect oyster ecology. Overall, the integration of dissolved oxygen into the C. virginica DEB model provides an important tool to make predictions about how oysters will respond to future oceanic and coastal deoxygenation.