Seasonal variation of dissolved oxygen, temperature and salinity in southern Brazilian coast (28 - 35ºS; 48 - 54ºW)

Abstract

The seasonal and spacial distributions of dissolved oxygen, temperature and salinity of surface and bottom waters over the continental shelf south of Torres, southern Brazil, were investigated from April 1968 to March 1969. The maxima and minima values of oxygen concentration in the upper layers were observed during the winter and summer along the coast (10-35 nm), respectively. Near the bottom this characteristics changes reflecting the northward advection of low oxygen water along the coast. For the sections along the continental shelf covering distances up to 100 nautical miles, the association of high oxygen concentration with low temperatures and low oxygen concentration with higher temperatures was also observed for distances no longer than 60 ran. Further east and below the surface layer, this tendency is modified by the advection of oceanic water from tropical and subantarctic origin. Near the coast, the oxygen maxima (5.0 ml/l) is associated with salinity values ranging from 30 to 33 (temperature values between 12 and 15ºC), indicating that (its occurrence) is probably due to the fresh water run-off from La Plata River. Some results of the changes in the nutrient concentrations during 1972 are also described.