The depth distribution of recent marine Ostracoda from the southern Strait of Magellan

Abstract. From 16 sediment samples collected from the Chilean part of the Strait of Magellan, 2338 Ostracoda were recovered. These represent 61 species belonging to 45 genera and 16 families. Previous work in the Tierra del Fuego Province has shown the faunas to be highly endemic, resulting from the relative isolation of the region and its particular climatic and oceanographical characteristics. The fauna of the Strait of Magellan is similar to those previously described with one notable exception: the occurrence of deep-water, psychrospheric species at shallow depths. Species of Bradleya, Agrenocythere, Poseidonamicus, Bythoceratina, and Legitimocythere, usually recorded from bathyal to abyssal depths of more than 1000 m, were found together in the same samples with a typical, shelf fauna. Such unusual depth distribution of psychrospheric species may have resulted from the extremely cold temperature and low salinity of the water in the southern Strait of Magellan, coupled with the upwelling of cold, deep water masses.