Latitudinal patterns and interannual variations of spring phytoplankton in relation to hydrographic conditions of the southwestern Atlantic Ocean

HÉCTOR F. OLGUÍN SALINAS; FREDERICO BRANDINI; DEMETRIO BOLTOVSKOY

HELGOLAND MARINE RESEARCH

SPRINGER

Lugar: Berlin; Año: 2015

1438-387X

The Southwestern Atlantic Ocean (SWA) includes the Confluence of Brazil and Malvinas Currents, which is one of the most energetic and variable regions in the world but with insufficiently known phytoplankton characteristics. The distribution and abundance of microphytoplankton, mainly diatoms, were assessed from subtropical to polar waters in a broad SWA area (34º-62ºS) in the austral springs of 1994 and 1995. The latitudinal patterns (50-m integrated data) in three springs, including our previous data of 1993, were interpreted with respect to the hydrographic conditions for the area during the survey periods. The biogeographic pattern of zones (Transitional, corresponding to the Brazil-Malvinas Current Confluence; Subantarctic and Antarctic Zones) and their limits (Subantarctic and Polar Fronts) emerging from these transects seemed to be a persistent feature, related to the hydrographic characteristics of this region. However, interannual changes in diatom assemblage structure (mainly in species richness, dominant species and dominance degree of assemblages with different ecological affinities) were detected, especially in the Transitional Zone, reflecting a colder spring in 1995 and a warmer spring in 1994 than usual. These changes agreed with reported differences in large-scale hydrographic conditions between 1993 and 1995, including a decreased diversity in 1995 due to a lower influence of subtropical waters.