Changes in organic matter from surface waters to continental slope sediments off the Sao Francisco River, eastern Brazil

Suspended matter, settling particles and sediments from the continental mar gin off the Sao Francisco, the largest river of eastern Brazil, were analyz ed for amino acids, hexosamines and carbohydrates. Their concentrations and spectral distributions are comparable to those observed in other marine re gions and exhibit variations which are related to the degree of dilution wi th lithogenic material. Preferential degradation and transformation of orga nic constituents within the water column during settling affect the nature and quantity of organic matter. The variations in the amino acid spectra in dicate that high bottom water oxygen contents and low sedimentation rates a re the factors responsible for severe degradation of organic matter at the sediment-water interface. (C) 1999 Elsevier Science B.V. All rights reserve d.