| Summary: | Trabajo presentado en el XVI Seminario Ibérico de Química Marina, celebrado en Cádiz del 24 al 26 de enero de 2012. During COUPLING cruise (January 2010) a detailed analysis of the inorganic nutrients concentrations (nitrate, nitrite, ammonium, phosphate and silicate) was conducted around the South Shetland Islands (SSI). The resulting patterns were discussed in relation to the different water masses and mesoscale structures presented in the study area. All macronutrients exhibited different patterns of variability, but had always concentrations high enough to be non-limiting for phytoplankton growth. The increment towards the south of silicate concentration (from to 26 to 80 μmol L-1), is the most significative trend. The lowest values were related with the Antarctic Surface Water (ASW). High values were detected in deep sites probably due to the opal accumulation. Si/N ratio fluctuated in the same way from 1:1 to over 4:1, afecting the proportion of diatoms. Phosphate concentration (mean 2 +- 0.2 μmol L-1) reached the highest values (> 2.3 μmol L-1) related with the Winter Water (WW). Anticiclonic eddies found in the middle of the Bransfield Strait delimited a convection cell of low phosphate (< 1.9 μmol L-1) and high nanophytoplankton biomass. Ammonium was restricted to the surface layer up to 200 meters. N/P ratio stated constant along the study area with values close to 15-16 except in the Antarctic Sound where the ratios increased to 18 and the microplankton size fraction dominated. The Fluorescence yield index was calculated as a proxy for Fe-stress (Hewes et al., 2009) showing a north-south gradient and a synergy with silicate for the development of the phytoplankton size structure community. In conclusion, despite being a high macronutrients concentration area, nutrients couple with physical features would exert a strong control to phytoplankton distribution around the SSI. Peer Reviewed
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