UN DECENNIO DI RICERCHE IDROCHIMICHE E IDROBIOLOGICHE SU LAGHI E POZZE DELLA VAL D’AVETO (APPENNINO LIGURE) A DECADE OF HYDROCHEMICAL AND HYDROBIOLOGICAL RESEARCH ON LAKES AND PONDS OF THE AVETO VALLEY (LIGURIAN APENNINES)

Resumen

A synthesis of the main results of hydrochemical and hydrobiological research carried out from 1988 to 1999 on lakes and ponds located at altitudes from 1267 to 1330 m a.s.l. in the Aveto Valley (Ligurian Apennines) is presented here. Special attention was devoted to the Lago degli Abeti, Lago Riondo and Lagastro pond, that are inside the area of the “ Riserva Naturale Integrale di Sopra Agoraie e Moggetto”, and the temporary ponds Asperelle and Code d’Asino. The research was widened to also include the Lago delle Lame, a lake located at 1060 m a.s.l.   Most of the waterbodies are magnesium and silica rich, due to the weathering of ophiolithic and sedimentary rocks that are prevailing in the area. Trophic status was evaluated using nitrogen and phosphorus concentrations and chlorophyll-a contents as well as the phytoplankton density and biovolume data; it is ranging from the oligotrophy of Lago degli Abeti to the eutrophic conditions of Lago Riondo and temporary ponds. The Lago delle Lame was heavily affected by the impact of human activities (fishing, tourism).   Zooplankton structure was characterised by different association patterns of the calanoids Eudiaptomus intermedius and Mixodiaptomus kupelwieseri with two species of Daphnia (D. longispina and D. obtusa). M. kupelwieseri is the only euplanktonic microcrustacean species living in the Lago degli Abeti, while it occurred in association with D. obtusa in the Asperelle and Code d’Asino ponds and with D. longispina in the Lagastro pond. Any calanoid species was found in the Lago delle Lame. Zooplankton of the Lago Riondo was dominated by E. intermedius and D. longispina.   Seasonal life cycles, reproductive strategies and genetic variability of M. kupelwieseri were carefully investigated: the populations inhabiting the water bodies with a more marked environmental instability (Lagastro, Asperelle and Code d’Asino) show the highest levels of genetic polymorphism.