Observations on phytoplankton distribution/size structure modulation by turbulence/dynamical stability and ageostrophic secondary circulation (ASC) in a no nutrient limited environment (Antarctica).

• Author: Pablo Sangrà, Universidad de Las Palmas de Gran Canaria.


• Names of other authors: C. García-Muñoz, B. Aguiar-González, C. Sobrino, B. Mouriño-Carballido, A. Marrero-Díaz, C. Henríquez-Pastene , A. Rodríguez-Santana, L. M. Lubián, C. M. García, M. Hernández-Arencibia, S. Hernández-León, E. Vázquez , S. N. Estrada-Allis.


• Oral or poster: oral.


• Downloadable abstract: click here.


• Downloadable presentation/poster: click here.


• Abstract:
  A high resolution interdisciplinary survey was conducted around the South Shetland Islands (SSI) during the austral summer 2010. We observed that the Bransfield Current (BC) recirculates around the SSI originating a mesoscale anticyclonic eddy at the tip of SSI and a thermohaline front (SF) along the north face of the SSI. Theses structures complete the previously reported components of the Bransfield Current System that includes the BC, a shallow frontal region (PF) and a system of anticyclonic eddies (AE) between both structures (Sangrà et al., DSR, 2011). We succeed to sample quasi-synoptically a transect through this rich mesoscale variability region that includes the PF, an AE, the BC and the SF. Nutrient samples indicate that phytoplankton growth could be limited by Iron only in those stations north of the SF. Phytoplankton properties distribution show a strong correlation with the physical environment linked to the above mesoscale structures. Mixed layer depth (MLD), turbulence profiler data and preliminary analysis of the dynamical stability combined with size-fractionated chlorophyll-a, Flow cytometry and FlowCam analysis suggest an increase/decrease of the percentage of large phytoplankton with the increase/decrease of the turbulence/instability degree of the physical environment. Chlorophyll concentrations well below the MLD and the euphotic layer suggest also a control of the phytoplankton distribution by ASC vertical cells at the BC and PF frontal regions.