A study of the Brazilian Fernando de Noronha island and Rocas atoll wakes in the tropical Atlantic

International audienc

Ichthyoplankton transport around the Brazilian Fernando de Noronha archipelago and Rocas Atoll: Are there any connectivity patterns?

812-818To investigate the influence of environmental conditions on ichthyoplankton transport in the FN and AR system, the outputs of a hydrodynamic simulation have been used as inputs to force an Individual-Based Model (IBM) around islands. The results show larval retention over the entire year. This retention is highly correlated with the intensity of the zonal current. Lagrangian analysis reveals connectivity between FN and AR, represented here by larval transport success, which would be important for the conservation of the species in these tropical Brazilian islands

Ichthyoplankton transport around the Brazilian Fernando de Noronha archipelago and Rocas Atoll : are there any connectivity patterns ?

To investigate the influence of environmental conditions on ichthyoplankton transport in the FN and AR system, the outputs of a hydrodynamic simulation have been used as inputs to force an Individual-Based Model (IBM) around islands. The results show larval retention over the entire year. This retention is highly correlated with the intensity of the zonal current. Lagrangian analysis reveals connectivity between FN and AR, represented here by larval transport success, which would be important for the conservation of the species in these tropical Brazilian islands

Seasonal cycle of nitrate in the euphotic layer of the Atlantic Cold Tongue

International audienc

Seasonal cycle of nitrate in the euphotic layer of the Atlantic Cold Tongue

International audienc

Seasonal cycle of nitrate in the euphotic layer of the Atlantic Cold Tongue

International audienc

Physical drivers of the nitrate seasonal variability in the Atlantic cold tongue

Ocean color observations show semiannual variations in chlorophyll in the Atlantic cold tongue with a main bloom in boreal summer and a secondary bloom in December. In this study, ocean color and in situ measurements and a coupled physical-biogeochemical model are used to investigate the processes that drive this variability. Results show that the main phytoplankton bloom in July-August is driven by a strong vertical supply of nitrate in May-July, and the secondary bloom in December is driven by a shorter and moderate supply in November. The upper ocean nitrate balance is analyzed and shows that vertical advection controls the nitrate input in the equatorial euphotic layer and that vertical diffusion and meridional advection are key in extending and shaping the bloom off Equator. Below the mixed layer, observations and modeling show that the Equatorial Undercurrent brings low-nitrate water (relative to off-equatorial surrounding waters) but still rich enough to enhance the cold tongue productivity. Our results also give insights into the influence of intraseasonal processes in these exchanges. The submonthly meridional advection significantly contributes to the nitrate decrease below the mixed layer