Zooplankton, Community composition, Ecological distribution, Siphonophora, Cnidaria, SW Atlantic, Brazil
Abstract
This work is based on the analysis of 99 zooplankton samples collected during the Oceanographic Expedition "ESPÍRITO SANTO I", held along the east coast of Brazil, between Cabo Frio and Abrolhos Archipelago, an area characterized by the occurrence of coastal upwelling, from July to September 1984. Zooplankton was collected with vertical plankton net hauls of 250 µm mesh size in the upper 200 meters layer. A total of twenty one species of Siphonophora was observed, two of which were identified as being physonect and the other as calycophorans. Specific diversity close to the shore and at the neighborhood of the Vitória-Trindade Bank System, showed smaller values, in comparison with those in the oceanic regions. Factorial analysis was used in order to access the changes observed in the population of the eleven most abundant species. The first two principal axes represented the influence of the nearshore - offshore gradient and the role of trophic interaction, accounted for 60% of the total variance of the data.
