COMPARISON OF POLYCHAETE COMMUNITY COMPOSITION FROM THE PATAGONIAN SHELF AND STRAIT OF MAGELLAN. PRELIMINARY RESULTS FROM CRUISES "SHINKAI MARU" IV, V, X AND XI (1978-1979) AND 2ND. P.N.R.A OCEANOGRAPHIC CRUISE (1991)
Bremec, C.1; Elias, R.2 & Gambi, M.C.3
1CONICET- Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP). c.c. 175 (7600) Mar del Plata, Argentina. 2 Departamento de Ciencias Marinas, Universidad Nacional de Mar del Plata.Dean Funes 3350 (7600) Mar del Plata, Argentina. 3 Laboratorio di Ecologia del Benthos, Stazione Zoologica "A. Dohrn", 80077 Ischia (NA), Italia.
The faunistic composition of benthic polychaetes from two different areas of the Magellanic Biogeographical Province were compared. One area comprises the Argentine continental shelf, from 50º to 55º S and between 92m and 192m depth, where 23 samples were taken during the "Shinkai Maru" cruises IV, V, X and XI. The other area corresponds to the Strait of Magellan, where polychaetes were recorded from 16 stations (30 to 800m), during the second "Programma Nazionale di Ricerche in Antartide" oceanographic cruise. Most of samples were taken from soft bottoms with dredges and sieved through a 1mm mesh screen. The most abundant benthic invertebrates on the Patagonian shelf were molluscs (41%), followed by, echinoderms (20%), crustaceans (19%), and polychaetes (9%). In the Straits of Magellan, crustaceans wre most abundant (47%), followed by polychaetes (35%), molluscs (9%) and echinoderms (5%). The total number of polychaete families identified from the patagonian shelf was 20, represented by 36 species. Most frequently sampled (43-65% sampling stations) and abundant families were Onuphidae, Nephtyidae and Ampharetidae, represented by Kinbergonuphis dorsalis, Aglaophamus sp., and Ampharete kerguelensis, respectively. In the Strait of Magellan, 34 families and 117 species of polychaetes were identified, most of them present only in 1-2 sampling stations. Syllidae (Exogone spp., Trypanosyllis sp. and Sphaerosyllis spp.), Ampharetidae (Melinna cristata) and Maldanidae (Maldane sarsi and Axiothella minor) were the most abundant families. Sixteen genera were recorded in both areas. Lumbriclymenella robusta, Travisia kerguelensis, Glycera papillosa, Kinbergonuphis dorsalis, Lumbrineris cingulata, Idanthyrsus armatus, Cistenides ehlersi, Ampharete kerguelensis, Amphicteis gunneriantarctica and Pista corrientis were identified to species; other genera present include Eteone, Harmothoe, Syllis, Aglaophamus, Drilonereis, and Euchone. Although identification of polychaetes is not completed to the species level, preliminary results indicate low similarity between zomes. Environmental differences along the Strait of Magellan, as compared to habitats sampled in the Atlantic Ocean, could explain, in part, the present results on geographic distribution of austral species.