Marine aquaculture off Sardinia Island (Italy): Ecosystem effects evaluated through a trophic mass-balance model

Marine aquaculture is an important growing worldwide industry. An ecosystem approach to study the effects of aquaculture on the Aranci Bay (Sardinia, Italy) was implemented by using a trophic mass-balance model in order to estimate the potential effects of finfish aquaculture and, therefore, to identify the species playing a key-role in ecosystem. Additionally, this study was used to evaluate the conflict between top predators and aquaculture. Mass-balance models were built using Ecopath software to characterize and compare the present state of the ecosystem versus a reconstructed past model representing the bay before the start of aquaculture activities. This modelling approach to the study of the fish farm activities in Aranci Bay has shown its appropriateness to describe the modifications induced, at an ecosystem level, by the nutrient loading into the area. Increased nutrient loading into the fish farm area may result in greater biological activity and may induce a strong coupling between the pelagic and benthic subsystems. Based on the results, the possible effect of top predators in the fish farm activities is not substantial. Furthermore, the use of mass-balance models can provide important additional information, complementary to the normal environmental assessment impact studies, before starting fish farm activities in an area.