STRUCTURE AND FUNCTIONING OF THE ANTHROPOGENICALLY TRANSFORMED COMACCHIO LAGOONAL ECOSYSTEM (FERRARA, ITALY)

Since 1985, the lagoons of Comacchio, in the coastal area of the NW Ad riatic Sea, have been experiencing an ecological catastrophe caused by an extremely dense bloom of picocyanobacteria. The bloom has resulted in a drastic depletion of all kinds of zooplankton, including protozo a. It has caused mass mortality of benthic fauna and the collapse of v aluable eel and mullet fisheries. The ecosystem of these lagoons, bein g thus completely transformed and deprived of animal components of its food web, appears to be remarkably stable on annual and seasonal scal es. Its main functional component is the phytoplankton community domin ated by several species of picocyanobacteria of the genera Coelosphaer ium, Aphanothece and Synechococcus. In this paper quantifications of t he main components of the plankton are presented together with data on standing stocks of organic matter and its cycling, and on the cycling of phosphorus and sulfur. The energy balances of the ecosystem are ca lculated and energy now schemes derived. The mechanism of the extreme stability of this new kind of aquatic ecosystem and a probable scenari o of its origin are discussed.