Monitoraggio a lungo termine e conservazione delle acque astatiche: i microcrostacei come bioindicatori funzionali dei cambiamenti del regime idrologico.

Microcrustacean communities (cladocerans and copepods) from astatic ponds of Castelporziano Presidential Estate were analysed to evaluate their role as group/species monitors of functional variations related to the wet phase duration, and to test their effectiveness in long term monitoring of hydrological modification of these biotopes possibly linked to climate changes. Samples from a set of 22 biotopes classified as permanent, semi-permanent and temporary ponds (based on the authors observations over a > 20 years time span, on the long term experienced Estate personnel, as well as on the results achieved by the wetland census performed during the years 1999-2001), allowed us to build an occurrence/absence data matrix of the species of cladocerans, calanoid and cyclopoid copepods occurring in Castelporziano, which was successively elaborated by adequate statistics. As a whole, 36 species of microcrustaceans (22 cladocerans and 14 copepods) were collected in the 22 ponds sampled. Cladocerans number of species per pond showed a higher variability (1 to 16 species) with respect to copepods (1 to 6 species). The Correspondence Analysis provided a good separation of two major hydrological groups , with permanent ponds more variable than the others. The separation, tested by means of ANOSIM, showed to be highly significant, while no correlation emerged among CA axes and species richness. The percent of similarity analysis (SIMPER) emphasizes the more responsible species for the similarity among biotopes of the same hydrological category: Eudiaptomus padanus etruscus and Simocephalus vetulus in permanent ponds; Alona nuragica, Megacyclops viridis, Simocephalus vetulus and Scapholeberis ramneri in semi-permanent ponds; Cyclops divergens, Daphnia chevreuxi and Diaptomus serbicus in temporary ponds. Our results highlight as: 1) long term data series are essential in providing an adequate knowledge of the species hosted in a certain area; 2) cladocerans and copepods possess a high power in discriminating ponds with different wet phase duration, showing to be very good functional biomonitors; 3) small astatic biotopes play an important role in biodiversity conservation, as they host high percentages of the species diffused in wider areas, besides of species exclusive for these habitats; 4) hydroperiod appears to be the main driving force in characterizing entomostracan assemblages in astatic ponds