Dynamics of lagoon ecosystems

Abstract

The dynamic behaviour of a lagoon ecosystem is investigated by using an eutrophication model. The phosphorous external load is assumed as control parameter. The response diagram, obtained by simulation, varying the value of control parameter, shows the existence of different ranges of stability of the ecosystem, characterized by the dominance of a specific group of primary produces and by a different ecosystem vulnerability to Summer water anoxia. A catastrophic bifurcation occurs for a critical value of the control parameter, which manifests as an abrupt change of the dominant specie from eelgrass to macroalgae. The serious consequences of such a selection in terms of eutrophication processes, anoxic crisis vulnerability and management policies for ecosystems subject to alternate states are emphasised.