Distribution of abundance, biomass, production and productivity of macrozoobenthos in the sub-Antarctic Magellan Province (South America)

Abstract

Distribution of abundance, biomass, productivity and production of macrozoobenthos was investigated in four study areas in the Magellan region (South Patagonian Ice-Field, Strait of Magellan, Beagle Channel, Continental Shelf). Using a Reineck box corer and a multibox corer, a total of 277 quantitative benthos samples were taken at 78 stations in water depths between 8 and 1139 m during the Joint Chilean-German-Italian Magellan "Victor-Hensen Campaign" in 1994, the "Polarstern" expedition ANT XIII/4 in 1996 and the Chilean expeditions "Cimar Fiordo II + III" in 1996 and 1997, respectively, on board RV "Vidal Gormaz". Mean abundance in the South Patagonian Ice-Field was significantly lower than in the Strait of Magellan and the Beagle Channel. Biomass and abundance decreased clearly with depth (20-300 m to 700-1500 m: 3.9 gC mm2 to 0.6 gC mm2; 2832 ind. mm2 to 569 ind. mm2). Average abundance, biomass and production of the whole Magellan region are lower (2318 ind. mm2, 3.2 gC mm2, 0.62 gC mm2 yearm1) than in the high Antarctic Weddell Sea. In the Magellan region, macrozoobenthos composition of abundance is mainly dominated by polychaetes (56%), followed by arthropods (16%), echinoderms (10%) and molluscs (11%). Comparisons of our present results with those of high Antarctic areas make it clear that the Magellan region has a transitional character.

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