Phytoplankton composition in the Weddell-Scotia Confluence area during austral spring in relation to hydrography

• Published in: Polar Biology
• Main Authors: Schloss, Irene R., Estrada, Marta
• Other Authors: Consejo Superior de Investigaciones Científicas (España)
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Springer 1994
• Subjects: Phytoplankton; Biomass Maximum; Phytoplankton Assemblage; Phytoplankton Composition; Hydrographic Condition; Austral; Gustavo; Weddell; Polar Biology
• Online Access: http://hdl.handle.net/10261/256145; https://doi.org/10.1007/BF00234969; https://doi.org/10.13039/501100003339

During the EPOS leg 2 cruise of the RV “Polarstern”, carried out in late austral spring of 1988–1989, the composition of phytoplankton in relation to the distribution of hydrographic parameters was studied in four successive transects carried out along 49°W and 47°W, across the Weddell-Scotia Confluence (WSC) and the marginal ice zone (which overlapped in part). In all transects, a maximum of phytoplankton biomass was found in the WSC, in surface waters stabilized by ice melting. Different phytoplankton assemblages could be distinguished. North of the Scotia Front (the northern limit of the WSC) diatoms with Chaetoceros neglectus, Nitzschia spp. and (Thalassiosira gravida) dominated the phytoplankton community. This assemblage appeared to have seeded a biomass maximum which occupied, during the first transect, an area of the WSC, south of the Scotia Front. The southernmost stations of the first transect and all the stations to the south of the Scotia Front in the other transects were populated by a flagellate assemblage (with a cryptomonad, Pyramimonas spp. and Phaeocystis sp.) and an assemblage of diatoms (Corethron criophilum and Tropidoneis vanheurkii among others) associated to the presence of ice. During the last three transects, the flagellate assemblage formed a bloom in the low salinity surface layers of the WSC zone. The bulk of the biomass maximum was formed by the cryptomonad which reached concentrations up to 4×10 cells l towards the end of the cruise. Multivariate analysis is used to summarize phytoplankton composition variation. The relationships between the distribution of the different assemblages and the hydrographic conditions indicate that the change of dominance from diatoms to flagellates in the WSC zone was related to the presence of water masses from different origin Financial support to M. E. was provided by a grant of the Consejo Superior de Investigaciones Cientificas of Spain. Drs. Demetrio Boltovskoy and Gustavo Ferreyra made important suggestions on early versions of the manuscript