Composition and structure of the invertebrate fauna in littoral sandy shores of Lake Bracciano (Central Italy) and water quality monitoring.

The invertebrate fauna associated with littoral sandy substrata in the volcanic Lake Bracciano (Italy), utlilized as water supply for the city of Rome, was analysed during one year in twelve sampling stations distributed along the entire lacustrine perimeter. The biocoenosis comprised 103 identified taxa belonging mainly to oligochaetes, chironomids, nematodes and cladocerans. Oligochaetes and nematodes constituted quantitatively most part of the collected organisms (76%), followed by considerable presence of copepods (13%). Several other groups have represented a smaller but important component, that have validly supported the diversification of the community. The analysis of a series of simple parameters (diversity indices, N/T ratio, densities of bioindicator taxa), that previous investigations have revealed as useful for a quality monitoring, provided a diagnosis of acceptable water quality in the marginal area of the lake, concurring to indicate a mesotrophic condition.