OCEAN-ATMOSPHERE DYNAMICS AND THEIR INFLUENCE ON THE PHYTOPLANKTON BIOMASS OFF THE MAGDALENA REGION COASTAL ZONE, COLOMBIAN CARIBBEAN

Abstract

From February to June 2008 at inshore sites of the Magdalena region, specifically in Gaira and Granate inlets and Taganga Bay, six field trips were done comparing the main dry and short rainy seasons. The main aim was to determine the coupled ocean-atmosphere influence on the upwelling intensity, considering the physical and chemical variability within the water column between 0 and 60 m and the response of the phytoplankton community measured as chlorophyll a. Atmospheric, oceanographic, and biological conditions were evaluated following the Eulerian method. According to the oceanic and atmospheric conditions during the research period, Ekman transport and continental upwelling processes occurred through February and April, in response to adequate conditions: average wind speed (>4.0 m/s) and wind direction (parallel and perpendicular to the coast). Physical and chemical anomalies were detected in the water mass, such as low temperature (25.34±0.82°C), high salinity (35.5±0.30) and oxygen subsaturation (70.6±7.8 %). The inorganic nutrient supply was higher during upwelling processes,consequently, the system was defined as mesotrophic, causing greater phytoplankton chlorophyll a biomass with level up to 1.60 μg/L. "La Niña" 2007/2008 event, which covered the period of this of this research, did not incite any important disturbance over the typical upwelling conditions.