Simulation model of Ulva rigida growth in shallow water of the lagoon of Venice.

The model presented here points out the possibility of simulating with a mathematical description the life cycle of Ulva rigida C. Ag. in the Lagoon of Venice. Model simulations allow the assessment of the relative importance of factors like light, temperature and nutrient availability on U. rigida growth. Particularly, phosphorus internal quota is shown to be always close to its maximum and thus it is never limiting while nitrogen limitation is weak and occurs only in the warm months. The influence of environmental disturbance, here represented by water movement and sediment resuspension induced by climatic events, is introduced in the model to simulate the observed sharp decline of biomass. Macroalgae biomass accumulation is not described in the model and its lack is claimed to justify some failure of the model when reproducing the biomass peak in the growing season. More knowledge is needed in this direction to understand better the influence that such factors could have on growth and distribution of U. rigida in shallow water areas of the Lagoon of Venice. The model has been implemented by following the object oriented paradig