A simulation model for the annual fluctuation of Zostera marina biomass in the Venice lagoon

Abstract

A simulation model was built to describe the growth patterns of Zostera marina in an area in the Venice lagoon. The model tracks changes in the above- and below-ground biomass and shoot density and is based on data for Zostera biomass, net production and growth rates, chemical-physical parameters and nutrient concentrations in water, sediment and particulate matter. It was assumed that the most important factors controlling Zostera growth and distribution are light and temperature, and that Zostera growth was not limited by nutrient availability. The goal was to simulate biomass production and its seasonal changes as a function of external forcing variables (light, water temperature, wind and tide-generated water movements) and internal control (plant density). A series of simulation experiments were performed with the basic model and its modifications showed that among the most important phenomena affecting Zostera growth are: (1) inhibition of production and recruitment of new shoots by high temperature and (2) light attenuation due to seasonal fluctuation and wind- and tide-induced suspension of sediments.