Spatial and temporal distribution patterns of Cladocera in the Argentine Sea

VINAS, MARIA DELIA; RAMIREZ, FERNANDO; SANTOS, BETINA; MARRARI, MARINA

HYDROBIOLOGIA

SPRINGER

Año: 2007 vol. 594 p. 59 - 68

0018-8158

The geographical and seasonal distribution of Cladocera was studied in the Argentine Sea, from the R ́ıo de la Plata River (34°S) to the Patagonian area (47°S). The cladoceran community included six species, which were found in the plankton especially in spring and summer and were absent during winter. Evadne nordmanni and Podon intermedius were the most widely distributed species, from 34°S to 44°S, in coastal and mid-shelf waters (MSW). Their Temperature-Salinity ranges of occurrence were around 8–21.7°C and 18– 36.4%. High numbers of E. nordmanni and P. intermedius were observed in the weakly stratified waters of the northpatagonian tidal front (42°S–45°S) compared to the other sectors of the frontal system. Pleopis polyphemo- ides mainly appeared north of 39°S in waters influenced by the R ́ıo de la Plata estuary (18–36.5%) and it showed preference for warm waters. Podon leuckarti was present only in a few samples from cold coastal and MSW between 38°S and 44°S and seemed to be a stenohaline species (33.4–34.2%). Penilia avirostris and Pseudoevadne tergestina were found north of 39°S particularly in coastal and MSW, but also in tropical and subtropical waters. Their Temperature-Salinity ranges of occurrence were 14–20.5°C and 27–36.5%. Although the highest densities of Cladocera were found in neritic waters, our data suggests that some species may also inhabit oceanic waters. During early spring, E. nord- manni, P. polyphemoides, P. intermedius, and P. leuck- arti were the first species to appear in the plankton in coastal waters off the Buenos Aires province, followed by P. avirostris and P. tergestina which gradually replaced the previously mentioned species and were dominant during the following summer. All species were absent during autumn and winter.