Macro-scale spatial distribution of microbial planktonic organisms in SW Atlantic and Antarctic contrasting marine systems

ALDER, V.A.; FRANZOSI, C.A.; SANTOFERRARA, L.F.; GÓMEZ, M.I.; LIZARRALDE Z; KATTNER, G.; LARA, R.J.

BUENOS AIRES

Simposio; 4 th OPEN SCIENCE CONFERENCE-SCAR; 2010

Scientific Committee on Antarctic Research

The study is aimed to improve the knowledge of the structure and ecologic role of planktonic microbial organisms (0.2-200 ìm) from contrasting marine systems (shelf, ocean, slope) characterized by different climatic (temperate, cold), oceanographic (Subantarctic-Antarctic), trophic status and biogeochemical regimes. The size and trophic structure and carbon contribution of 11 taxonomic groups of bacteria, algae, protozoa and metazoan larvae and 15 environmental parameters were analysed from sub-surface samples collected during late austral summer along a latitudinal transect covering Patagonian waters (Argentine shelf), the Drake Passage and the Western Antarctic Peninsula (WAP). The following main trends were observed: 1) A similar heterotrophic/autotrophic cells density ratio (67/33 %) throughout the studied area, with the exception of one single site located in Antarctic waters where diatoms (111 ìg C L1) prevailed over heterotrophic components (57 ìg C L1); 2) Significant negative correlations between density/biomass of both autotrophic and heterotrophic cells with phosphate and Total Dissolved Nitrogen; 3) A pronounced coupling between biogeochemical zonation and that derived from densities of main taxonomic groups: The two main groups of stations were in correspondence with shelf Patagonian waters and Drake Passage plus WAP. These zones were characterized, respectively, by a shift from small to large phytoplankton and from low to high silicate, nitrate, chlorophyll, POC and PON; 4) Total microbial biomass values, instead, reflected two groups of stations in correspondence with Subantarctic and Antarctic waters. The interactions explored are expected to contribute to the understanding of C an N cycles, trophic web functioning and climate models. . . .