engleski

Zooplankton in small fishless Adriatic ponds (Mediterranean Sea)

Mediterranean ponds have been identified as vulnerable and threatened habitats of major priority in the EU Habitats Directive. Despite small size these ephemeral waterbodies are recognized as reservoirs of biodiversity for aquatic invertebrates. The main goal of our investigation was to establish most important biotic and abiotic factors that shaped zooplankton in small ponds. We sampled zooplankton from nine small ponds situated on Dugi otok island (middle Adriatic Sea, Croatia). According to their hydroperiod they can be classified as temporary long ponds with annual summer drying, or semi-permanent ponds, which dry every few years. Odonata larvae dominated in macrozoobenthos and also these habitats are suitable for Bufo viridis Laurenti, 1768 tadpole development. Altogether 56 different species were found in zooplankton. Rotifera were most diverse group of zooplankton (40 taxa), followed by Cladocera (10) and Copepoda (6). Among rotifers prevailed Anuraeopsis fissa (Gosse, 1851), Epiphanes senta (Müller, 1773), Keratella testudo (Ehrenberg, 1832), Lecane bulla (Gosse, 1851), Lecane closterocerca (Schmarda, 1859) and Trichocerca pusilla (Jennings, 1903), representing up to 96% of the total rotifer abundance. Small bodied cladocerans dominated in these ponds, and three species were most abundant: : Alona rectangula Sars, 1861, Chydorus sphaericus (O.F. Müller, 1776) and Moina brachiata (Jurine, 1820). Of copepods, Eucyclops serrulatus (Fischer, 1851) was most abundant species. Nauplii and copepodites stages were present in almost all waterbodies in high density. The most important biotic factor that shaped cladoceran and copepods assemblage was macrophyte abundance. Rotifers showed a dual response to the presence of macrophytes: semiplanktonic species (e.g. Lecane spp.) preferred macrophyte stands while planktonic species (e.g. A. fissa, K. testudo, T. pusilla) were more abundant in ponds with low macrophyte cover. Salinity was one of the most important abiotic factors in shaping these assemblages and the species richness of zooplankton decreased with increasing salinity. On the Mediterranean islands small, shallow ponds are often the only freshwater habitats. It is necessary to implement their continuous research and to undertake appropriate conservation and restoration measures, in order to prevent their succession primarily because these are important (micro)habitats for biological and landscape diversity.

Rotifera, Cladocera, Copepoda/ karst lake, permanent and temporary ponds/feeding groups

nije evidentirano