Southern coastal system of the San Jorge Gulf during spring

PIERATTINI MARTÍNEZ, REGINA; PISONI, JUAN P.; PAPARAZZO, FLAVIO E.

ECOLOGÍA AUSTRAL

ASOCIACIÓN ARGENTINA DE ECOLOGÍA

Año: 2023 vol. 33 p. 325 - 336

0327-5477

The San Jorge Gulf was declared an area of national economic, commercial, conservation anddiversity interest. To contribute to its study, the southern coastal sector of the gulf was characterised in physicaland chemical parameters in spring campaigns (November 2016 and 2017). Samples were taken on board theoceanographic vessel Puerto Deseado in three transects perpendicular to the coast and another one to thesoutheast of the gulf, which crosses a thermohaline front. The transects perpendicular to the coast showeda similar pa􀄴ern of distribution of physical and chemical properties in the water column. At the nearshorestations, the water column was homogeneous and the nutrient concentrations between the surface and bo􀄴omlayers were similar. At offshore stations, the water column was stratified and the nutrient concentrationswere higher in the bo􀄴om layer than at the surface. In 2016, a wind upwelling front was observed in thesouthwest of the gulf. On the transect crossing the thermohaline front, the difference between the two sides ofthe front was not well visible. Throughout the study area, silicic acid and nitrate limited primary production.Satellite chlorophyll-a data and fluorescence profiles showed that the southern sector of the gulf has a highbiomass of phytoplankton during November. We conclude that the southern sector of the SJG has differentfeatures depending on the external forcing caused by the front. The presence of fronts stimulates the growthof phytoplankton biomass through the injection of nutrients from the homogeneous part to the stratified part.This would affect phytoplankton community and, thus, the productivity of the system.