Microbiological characterization of a semi-enclosed sub-Antarctic environment: the Straits of Magellan.

Among sub-Antarctic ecosystems, the microbiology of the Straits of Magellan has been poorly documented due to the scarcity of observations. In this context, the spatial distribution of microbiological parameters, both in terms of abundance (total picoplankton and picophytoplankton, cultivable heterotrophic bacteria) and biochemical assays (adenosine triphosphate and lipolysaccharide estimations, as well as electron transport system activity), was investigated in the epipelagic layer along the Straits during late summer 1991 and early autumn 1995. The microbial dynamics showed significant variations along the Straits, with increasing values generally determined eastward both in 1991 and 1995. Microbiological results were additionally correlated with available data on the physico-chemical and biological properties of the analyzed water masses. Taking into consideration the whole dataset, the principal component analysis led to the identification of three main macro-areas along the Straits of Magellan (Paso Largo, Paso Ancho and Angostura/Isla Isabel) with different trophic features. This held true when the two cruises were individually considered, as well as when comparing each macro-area between the two cruises. Additionally, a first attempt to quantify the carbon flux through the microbial compartment within the main identified macro-areas was made. The present work will allow the gaining of further understanding of the microbiology of this under-investigated sub-Antarctic marine ecosystem.