The aim of this study is to provide a synthesis of the present knowledge of the marine Porifera in the Southwest Atlantic between 35º S and 56º S, and between the coast of Argentina and 50º W. The analysis of 34 taxonomic publications produced a list of 149 oceanographic stations and 28 coastal localities with records of Porifera for the study area. A total of 196 species, 5 subspecies and 1 variety of marine sponges was recorded, 187 of which belong to the Demospongiae, 10 to the Calcarea and 5 to the Hexactinellida. The most widely distributed sponges in the study area are Dasychalina validissima, Iophon proximum, Mycale magellanica, Tedania massa and Tedania spinata, all Demospongiae. The sampling effort was unequally distributed, reaching a maximum concentration off Buenos Aires Province and around the Malvinas/Falkland Islands. The biodiversity of marine Porifera of Argentina along 21 degrees of latitude is closely related to the concentration
of the sampling effort. It appears to be highest in thoroughly surveyed areas, such as around Mar del Plata, Port Stanley and the coast of Tierra del Fuego. No correlation was found between species number and depth. The richest stations were recorded around 130-140 m. Biodiversity of Porifera is weakly but significantly correlated with latitude, since stations between 50º S and 55º S were on average richer than those located off Buenos Aires Province. Knowledge of the geographic distribution of marine Porifera in Argentina is fragmentary. Much more basic information is needed, particularly for the continental shelf off Río Negro and Chubut Provinces.
South West Atlantic ( =only warm temperate; cold temperate see *SUB)