BIOLOGICAL DIVERSITY AND BIOGEOGRAPHY OF THE ZOOPLANKTON OF THE SOUTH ATLANTIC

BOLTOVSKOY DEMETRIO; CORREA NANCY

Mar del Plata, Argentina

Congreso; Joint Assemblies of the IAPSO & IABO (An Ocean Odyssey); 2001

BIOLOGICAL DIVERSITY AND BIOGEOGRAPHY OF THE ZOOPLANKTON OF THE SOUTH ATLANTIC Nancy M. Correa y Demetrio Boltovskoy   To date, approximately 7000 marine zooplankters have been described for the World Ocean, and probably at least twice as many species are still awaiting to be described. So far only 35-40% of this inventory was found in the South Atlantic, but our estimates indicate that the actual fraction of world-wide zooplanktonic taxa which are effectively present in this area (0 to 60ºS, from the American to the African coasts) is close to 60%. Of all the species recorded in the South Atlantic, the tropical area hosts 72%, the subtropics 78%,  the transitional waters 57%, the subantarctic 39%, and the antarctic 20%. Only 2 to 8% of the zooplankters are restricted to just one of the major biogeographic areas; most are present in at least two adjoining areas, and somewhat fewer dwell in three contiguous areas. The specific richness of the tropical-subtropical belt is 3-4 times higher than that of polar and subpolar waters, but the number of species restricted to the warm waters is almost 10 times higher than that in the cold waters. From north to south, in the transition is where zooplanktonic diversity values drop most abruptly: the boudaries of this biogeographic area have ca. twice as many distributional breaks as the tropical-subtropical and the subantarctic-antarctic boundaries. This transitional barrier not only affects a large number of species, it also is much wider geographically, covering about 12-14° in latitude.   Joint Assemblies of the IAPSO & IABO (An Ocean Odyssey), Mar del Plata , 21-28 octubre