ECOLOGICAL RESEARCH ON THE ANIMAL COMMUNITIES OF THE PO RIVER DELTA LAGOONS

The main results of research on invertebrate biology and ecology in the lagoons of the Po River Delta (Sacca del Canarin, Sacca di Scardovari, Sacca di Goro) are presented and related to the more significant approaches followed in ecological research during the last two decades. The lagoons, which are intrinsically eutrophic water bodies, have recently undergone intense eutrophication due to the dramatic increase in the Po river nutrient loading. A shift towards a dystrophic state was indicated by the appearance of large Ulva rigida beds in spring and by extensive anoxia during the summer due to the decomposition of the huge macroalgal biomass. Particularly severe dystrophic crises occurred in the Sacca di Goro. Zooplankton and zoobenthos changes were analyzed according to the variations in hydrographic features as well as those in the trophic state of the water. The significance of population dynamics studies in evaluating biological responses to environmental stresses is emphasized. Investigations on animal populations and communities may be advantaged by maintaining the ecosystem approach as a stimulating frame of reference, but, at the same time, by developing specialized and problem-oriented research. The expansion of knowledge on nutrient cycling and related microbial processes in the lagoons could significantly improve the analysis of the ecological role of animal communities. A trend towards using experiments both in the laboratory and in the field must be encouraged. Finally the need for long-term studies is stressed. Pluriannual series of density data of both plankton and benthos communities have been collected in Sacca del Canarin and Sacca di Goro.