Zonal variability of pelagic Siphonophora (Cnidaria) in the atlantic sector of the southern ocean

Abstract

Siphonophores have a widespread distribution in the world oceans, can be very abundant in some areas, and can have a significant impact on other pelagic animals. In this work, siphonophores from the Atlantic sector of the Southern Ocean were studied. Zooplankton organisms were collected at 35 stations in December 2009. Thirty different species were found: 2 physonects and 28 calycophorans. Total abundances of siphonophores varied with latitude; maximum numbers were observed in the northern part of the transect, in the vicinity of South Africa, where Muggiaea atlantica was the dominant species. To the south, the contribution of Eudoxoides spiralis and Lensia subtilis increased. In the whole investigated region, the most numerous siphonophore was Dimophyes arctica. Based on our results, it can be assumed that in the Atlantic sector of the Southern Ocean probably exist two Siphonophora biodiversity spots, probably exist in the Benguela Current region and the Subtropical Convergence region. Moreover, our results show that the Southern Subtropical Convergence seems to be a very strong biogeographical barrier for many tropical and temperate Siphonophora species.