A TROPHIC MODEL FOR ULVA-RIGIDA IN THE LAGOON OF VENICE

This paper focuses on a model of the life cycle of the macroalgae whic h can be considered one of the most important and earliest steps of a more general environmental modelling activity for the Lagoon of Venice . The variables considered by the model are the algal biomass, and the intracellular quota of nutrients (nitrogen and phosphorus). The model simulates a point in the Lagoon. Because of this, other factors, such as external nutrients and dissolved oxygen concentrations, are consid ered as input data and evaluated by monitoring the water quality. The model is calibrated with a time series of weekly data collected during the years 1985 and 1986. The model allows for a deep knowledge of the macroalgae life cycle in the Lagoon and points out the relevance of s ome processes or factors like: nitrogen limitation; control of algal d ecay due to oxygen depletion; relevance of the combination of photosyn thesis, temperature and nutrient effects.