Development of a numerical model to study the dispersion of wastes coming from a marine fish farm in the Ligurian Sea (Western Mediterranean)

In order to simulate the dispersion of pollutants released from a marine fish farm in the Ligurian Sea (Western Mediterranean), the Lagrangian particle model LAMP3D has been nested into the numerical hydrodynamical model POM. Estimates of the regional dispersion patterns of nitrogen, phosphorus and organic carbon were calculated using a three-dimensional mesoscale grid and compared to in situ experimental data. In the numerical simulations, the dispersion of different aquaculture wastes (dissolved nutrients, faecal matter and feed wastes) was evaluated by changing the rates of particles settling and their condition of release (continuous or periodical). Results of the simulations clearly showed that dissolved particles tend to spread rapidly and undergo rapid dilution depending on dominant wind and surface currents direction. In contrast, settling particles remain mainly confined in the fish farm area and readily sink. Predicted concentrations of wastes were low in both the water column and sediment compartments and never exceed the threshold of environmental crises.