Factors affecting macroinvertebrate communities in astatic ponds in central Italy

Twenty astatic ponds near Rome were studied in order to define the relationships between physicochemical variables and macro invertebrate communities. The main abiotic factor differentiating the ponds was the annual hydrologic cycle. Depth, surface area, and sand percentages in the sediment were higher in permanent ponds, whereas silt+clay content was higher in temporary ones. No difference was recorded in pH, conductivity and oxygen content in the water or organic matter in the sediments between the two pond types. Three main ecological assemblages were distinguished: a) generalist taxa common to both pond types; b) taxa associated with and adapted to temporary ponds; and c) taxa which seemed to prefer permanent ponds. Overall, there was no relationship between number of taxa and surface area, except for Odonata and aquatic macrophytes. A positive correlation was observed between number of macrophyte species and macro invertebrate taxa richness, and particularly of odonates and chironomids, suggesting that an increase in aquatic vegetation species leads to an increase in microhabitats and suitable food, substrate, and/or refuge from predators. Odonata seemed also to prefer more stable and sunny ponds.