Surface macronutrient dynamics of the Drake Passage and the Argentine Sea

FLAVIO E. PAPARAZZO; JOSÉ LUIS ESTEVES

Plankton Ecology of the Southwestern Atlantic - From the Subtropical to the Subantarctic Realm

Springer

Año: 2018;

The dynamics of macronutrients on the surface is key for marine life. In this work, we focus on the nitrate, phosphate, and silicate distribution along the Drake Passage and the Argentine Sea. These nutrients have the highest concentration in the south of the Drake Passage because of upwelling of deep waters and inlets of coastal currents. The Antarctic Convergence forms a kind of barrier between water masses, greatly limiting the surface exchange of chemical species to the north. Pacific Ocean waters mixed with surface waters located north of the Polar Front enter the Argentine Sea giving rise to the Patagonian and Malvinas Currents. On their way, primary producers deplete nutrients and, at a given moment, nitrate reaches limiting concentrations. Two processes locally modify the resulting N-S nutrients gradient: 1) The shelf offshore component receives the contribution of the nutrient-rich Antarctic waters, which move northward along the continental slope through the Malvinas Current; 2) Large tidal waves and their interaction with the seabed create seasonal frontal systems that increase the chemical species concentration near the coast. The discharge of the less saline waters of the Magallanes Strait can be observed up to 43°S, but its effect on macronutrients is low. Patagonian rivers present a low flow and seem to make only local contributions. Until now, the fertilization effect of submarine groundwater discharge is unknown and the aeolian dust input is under study. The ice pack coverage in the Drake Passage and the water column stratification in the Argentine Sea govern the seasonal variation. Interannual differences have been associated with ENSO-like events, but information is not enough to draw conclusions. Due to the importance of knowing the nutrient dynamics to understand the biological processes of the region, multidisciplinary studies focusing on this topic should be promoted.