In the South Atlantic nearly the Brazilian coast, at low latitudes, the layer of minimum oxygen concentration shows distinct values between the Equatorial region (7ºS) and the region limited by latitudes of 18-22ºS. In the vicinity of the Equator the minimum concentration is remarkably clear (2,0 ml/l at 7ºS) and at 22ºS the minima values raise up to 4.0-4.5 ml/l. The minimum oxygen layer follows the isopynics surfaces (σt = 26.8-27.2) in depths of 300-400 m (7ºS) and 600-800 m (22ºS) . The oxygen concentration in this area results from a biochemical and physical processes, due to the presence of poor water Brazil Current southward and the rich one Intermediate Antartic water flowing northward.