Observation of regeneration of nitrate, phosphate and silicate during upwelling off Ubatuba, Brazil, 23°S

Off the Brazilian coast near Ubatuba, an upwelling event of South Atlantic Central Water (SACW) has been observed that transfer nutrient-rich water from 300 to 400 m depth onto the continental shelf to depths less than 35 m. Earlier work showed that SACW is present on the shelf quite frequently; however, nutrient data as natural tracers of water masses, are largely undocumented so far. During the upwelling process the water advanced over the shelf increasing its nutrients concentrations and depleting its content of dissolved oxygen due to the regeneration process. The ratios of regeneration relative to their open ocean origin amount to 4.6 μM for nitrate, 0.43 μM for phosphate and 5.7 μM for silicate on average, while the dissolved oxygen depletes by 114.9 μM.