A fully-spatial ecosystem-DEB model of oyster (Crassostrea virginica) carrying capacity in the Richibucto Estuary, Eastern Canada

•A DEB model for Crassostrea virginica was parameterized.•Shellfish carrying capacity was explored by using an ecosystem model.•Natural variation in phytoplankton is a benchmark for ecological resilience.•Bay-scale depletion index is used to determine sustainable standing stock biomass.

The success of shellfish aquaculture as well as its sustainability relies on adjusting the cultured biomass to local ecosystem characteristics. Oyster filter-feeding activity can control phytoplankton concentration, reaching severe depletion in extreme situations, which can threaten ecological sustainability. A better understanding of oyster–phytoplankton interaction can be achieved by constructing ecosystem models. In this study, a fully-spatial hydrodynamic biogeochemical model has been constructed for the Richibucto Estuary in order to explore oyster carrying capacity. The biogeochemical model was based on a classical nutrient–phytoplankton–zooplankton–detritus (NPZD) approach with the addition of a Dynamic Energy Budget (DEB) model of Crassostrea virginica. Natural variation of chlorophyll was used as a benchmark to define a sustainability threshold based on a resilience framework. Scenario building was applied to explore carrying capacity of the system. However, the complex geomorphology of the Richibucto Estuary and the associated heterogeneity in water residence time, which is integral in estuarine functioning, indicate that the carrying capacity assessment must be specific for each area of the system. The model outcomes suggest that water residence time plays a key role in carrying capacity estimations through its influence on ecological resistance.