Effect of Changes in Seasonal Rain Regime on Coastal Ecosystem Structure and Aquaculture Activities

A downscaling experiment linked climate forcing produced by a Regional Climate Model for Europe to a 3D high resolution coupled transport biogeochemical model for the Lagoon of Venice, which in turn forced: a) a food web model for evaluation of cascading effects on ecosystem structure and b) a population dynamic bioenergetic filter feeders bivalvae model for evaluation of effects on aquaculture activities. The hierarchy of models was used to compare result for a reference situation (RF, 1961-1990) with results for two future IPCC scenarios (2071-2100), representing market oriented and local sustainability policies (scenarios A2 and B2, respectively). Future climate projections suggest that, locally, annual mean rain will not change much but the seasonal patterns will likely do so. Summer and spring will be more dry and winter and autumn more rainy. This will potentially increase winter nutrient concentrations but -because of unfavourable timing - primary and secondary productions will decrease, and nutrient surplus will be exported from the Lagoon of Venice to the Adriatic Sea. The impacts on higher trophic levels could be softened thanks to presence of alternative energy pathways and role of omnivory. However, in our future scenario of the lagoon food web the suitability for higher trophic level organisms seems lower. A more detailed analysis on clam aquaculture indicates that this activity will suffer the decrease of primary productivity, and point to the need of implementation of proper aquaculture management policies. In the light of adaptive management. These policies cannot be a straightfoward extrapolation of present practises, but need to be defined basing on future conditions.