Some chemical aspects of the marine environment off the Amazon and Pará rivers, Brazil

Abstract

This paper describes the salinity, temperature, dissolved oxygen and inorganic phosphate distributions for the Brazil northern coast, with special reference to the marine environment off the Amazon and Pará rivers. The change in direction of the coast with the consequent change in the axis of the Guiana Current together with the large amount of suspended matter contributed by river waters, create peculiar conditions on the continental shelf. These conditions are also influenced by the wind and rain system. Out from the continental shelf Tropical Atlantic oceanic conditions are prevalent. In contrast to the very low fertility of the Guiana Current the coastal waters, directly influenced by the rivers, show a supersatu ration of dissolved oxygen. The nutrients absorbed by suspended matter are partly liberated when the rivers mix with the oceanic water. However, the low light penetration restricts the oxygen production to only few meters.

Influence of the Amazon and Pará Rivers on Water Composition and Phytoplankton Biomass on the Adjacent Shelf

“…An increase of dissolved oxygen values nearshore (values up to 5.23 ml O 2 L Ϫ1 ), close to the Amazon estuary, was also detected by MAGLIOCCA (1971). This pattern was also observed by GESSNER (1962), who found high values of oxygen saturation at the mouth of the Amazon.…”

Spreading of the Amazon River Plume

“…The ocean in this part of the shelf is shallower than 20 m, where the vessel could not enter. The curve of the northern coastline here forces the fresh water from the Amazon River to run closer to the coast and be reinforced by the outflow [Magliocca, 1971]. Judging by the spatial distribution of salinity recorded during field works, the stations of the study area were mostly in the offshore part of the Amazon River plume and its periphery above the continental slope, as well as the outer water area of ocean waters.…”

Seasonal dynamics of nutrients in an Amazon estuary

“…Na foz do estuário do rio Amazonas, observou-se concentrações de OD semelhantes ao estuário do rio Paracauari: como 5,23 mg.L-1 detectado por Magliocca (1971) e 6,54 mg.L-1 por Santos et al (2008).…”