Long term simulations of population dynamics of Ulva r. in the lagoon of Venice

The dynamic of macroalgae is implemented in a 3D transport-water-quality model of the central part of the lagoon of Venice. Ulva biomass density and nitrogen concentration in Ulva tissue have been added to the set of state variables previously considered, that is to phytoplankton and zooplankton densities, concentrations of nutrients in water, detritus and dissolved oxygen. The model shows that Ulva succeeds in the competition with the phytoplanktonic community in the shallower areas, where water temperature and irradiance levels reaching the bottom are sufficient to sustain growth. Long term evolutions of Ulva colonies, under different scenarios of forcing functions, show that adverse meteoclimatic conditions can be more effective in reducing Ulva biomass than a consistent decrease in the loads of Nitrogen.