Zooplankton abundance and diversity in Lake Bracciano, Latium, Italy

The zooplankton community structure in Lake Bracciano (Latium, Central Italy) was studied in monthly surveys throughout an annual cycle (November 1998 – October 1999). The seasonal cycles and population dynamics of the dominant species are described and discussed. Copepods numerically dominated the community throughout the study period with calanoid Eudiaptomus padanus etruscosexsetosus making up the largest share of zooplankton density; moreover it accounted for the largest portion of total biovolume. Cladocerans represented a significant component of the zooplankton in the summer and autumn months. No substantial differences in regard to results of previous investigations (1971, 1972, 1984) were observed. The only differences for which there is evidence consist of the appearance of Filinia terminalis, never previously found in the lake, and the replacement of Keratella cochlearis instead of Kellicottia longispina as dominant species. However, the results of the comparison of the different investigations confirm that the trophic state of the pelagial region may be classified as oligo-mesotrophic.