Ecosystem maturity as a proxy of mussel aquaculture carrying capacity in Ria de Arousa (NW Spain): A food web modeling perspective

As demand for global food security increases and arable land decreases, utilization of marine ecosystems intensifies. In particular, coastal marine ecosystems which are easily accessible, highly productive, and often protected from large storm perturbations, make ideal areas for expansion in ocean food systems. Whether an ecosystem has been identified as a potential new site for food production or whether it has had long-established food production activities, proper management of resources is paramount for sustainability of both the eco-system and food industry. One way to approach sustainable management is by taking a carrying capacity approach using food web modeling. Our study area focuses on a highly productive estuarine embayment that has had long-standing practices of both mussel aquaculture and artisanal fisheries since the 1960's. Using ecological modeling with Ecopath software, we have calculated the current ecological carrying capacity and production carrying capacity of the system. Complementing this new analysis, we performed a review of ecosystem ecology indicators to compare relative carrying capacities. We found that current mussel aquaculture biomass (1718 t km(-2)) have exceeded ecological carrying capacity (773 t km(-2)) but it is still below production carrying capacity (2164 t km(-2)). Based on Ecopath maturity index and omnivory index output values, Ria de Arousa can be considered a mature ecosystem relative to other coastal and estuarine systems. This high level of maturity may be interpreted as the resilience of this system to cope with changes brought about over time by the intensification of food production and human activity.