Distribution and ecology of calanoid species in relation to morphometric and chemical characteristics of lakes and ponds of the Northern Apennines (Italy)

In 1999 a limnological campaign was carried out in 89 water bodies located in 8 valleys of the Northern Apennines (provinces of Genua, Piacenza, Parma and Reggio Emilia) at an altitude between 877 and 1772 m a.s.l. This survey took into account permanent lakes, but also temporary and ephemeral water bodies which had been scarcely considered in hydrobiological studies previously carried out in this area. Most of the biotopes were visited seasonally during the ice-free period (May - November). The aim of this research was to define the relationships between morphometric features, lithology, hydroperiod and chemical characteristics of the biotopes and the distribution of the three species of calanoid copepods reported in the Northern Apennines, i.e. Mixodiaptomus kupelwieseri, M. tatricus and Eudiaptomus intermedius. The two most common species, M. kupelwieseri and E. intermedius, show an overlap in their altitudinal distribution. However, the former species widely occurs in very shallow, temporary or ephemeral water bodies and the latter clearly prefers permanent, relatively deep waters. Also the water inonic concentration influences the distribution of these two diaptomids, while concentrations of dissolved inorganic nutrients seem to have a negligible effect. Mixodiaptomus tatricus was found only in two shallow ponds beyond 1700 m a.s.l. Co-occurrence of E. intermedius and M. kupelwieseri has been observed only in a pond, but the two species are not found at the same time. The proportion of subitaneous and resting eggs laid in different seasons was analysed in populations of E. intermedius. The voltinism of this species varies according to the duration of the filling period and the productivity of the water bodies. The persistence of diaptomids in the study area has been evaluated through the comparison with distributional data available from the 1950s for most of the permanent lakes and some temporary habitats. Populations appear to be stable over time also in scarcely predictable environments as temporary pools, although in some cases calanoids have disappeared from biotopes severely affected by anthropogenic impacts.