Multiannual trends in fronts and distribution of nutrients and chlorophyll in the southwestern Atlantic (30-62°S).

BRANDINI, FREDERICO; BOLTOVSKOY DEMETRIO; PIOLA ALBERTO; KOCMUR SANTIAGO; ROTTGERNS R; ABREU PAULO

DEEP-SEA RESEARCH. PART 1. OCEANOGRAPHIC RESEARCH PAPERS

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Boston; Año: 2000 vol. 47 p. 1015 - 1033

0967-0637

This paper presents the first data on the vertical distribution of chlorophyll and nutrients in the upper layers of the southern Southwestern Atlantic, in relation to frontal systems and the general hydrographic features. The survey covered quasi­simultaneously the area between 30 and 62°S, at the beginning of the austral summer of 3 consecutive years (1993 through 1995). Our results show a rather stable oceanographic structure, with similar patterns of latitudinal chlorophyll and nutrient distributions. An outstanding feature present throughout the three seasons covered are two zones of high phytoplankton production, where bloom chlorophyll concentrations of >1 µg/l seem to occur frequently. The first area is the upper euphotic zone of the Brazil-Malvinas Confluence zone between approximately 36 and 50°S. The second chlorophyll-rich zone is centered on subsurface layers of the Antarctic Surface Water south of the Polar Front as far as 62°S. The rest of the area covered shows low chlorophyll concentrations, either due to nutrient limitation (subtropical waters of the Brazil Current), or to excessive turbulence and upper-layer instability (Malvinas Current). The occurrence of a permanent meander around 38°S was noticed in coincidence with the cyclonic retroflexion of the Malvinas Current, causing upwelling of deep water. The ecologic implications of this eddy-induced upwelling are discussed.