Nictemeral variation in an oceanography station in the Amazon continental shelf

Abstract

During the Operations Oceanography’s North III and North IV (program REVIZEE), samples of water were collected for 24 hours, in a period by three hours, on May 20, 1999 (period of maximum discharge of the Amazon’s river) and August 13, 2001 (transition period of the Amazon’s river), in a located station in the Amazon Continental Shelf. The objective of this work was to evaluate the variation of parameters abiotics and chlorophyll a, during that nictemeral collection. On August 13, 2001, the smallest salinity variations (of 34,0 and 36,4) and the smaller concetrations of nitrate (medium of 1,7 μmol.L-1) and of phosphate (medium of 0,2 μmol.L-1) were detected and the largest chlorophyll a concetrations (maximum of 5,47 mg,m-3). While on May 20, 1999, the largest concentrations of nitrate were detected (medium of 4,9 μmol.L-1) and phosphate (medium of 0,4 μmol.L-1), and largest variations of salinity (minimum of 20,0 and maximum of 35,6) and concentrations of chlorophyll a (maximum of 0,32 mg.m-3), that indicates be the transparency of the water the limiting factor for the development of the primary productivity , in the area of the Amazon Continental Shelf.