Geo-chemical and optical characterizations of suspended matter in European coastal waters

Suspended particulate matter of various marine European coastal waters has been the subject of geo-chemical and optical characterization during a series of oceanographic surveys in 1998. The Loire, Seine, Thames, Rhine, Humber, and Weser/Elbe River plumes were sampled in May 1998. Another survey was conducted in September 1998 in the English Channel (Plymouth coast), North Sea (Texel area), German Bight, and the Baltic Sea. Variations and covariations in total particulate carbon (TPC), particulate organic carbon (POC), particulate nitrogen (PN), and total suspended matter (TSM) have been examined. The POC: PN ratio was found to be variable within the sampling sites. The high POC: PN ratio (average¼9.6) observed in the Baltic Sea probably reflects the peculiar nature of this water body, characterized by a high content of organic matter in TSM as well as in the dissolved phase. The TSM demonstrated to be an effective tracer for POC in the North Sea and in the Baltic Sea, and, generally, for the noncarbonatic inorganic matter (NCIM) because of the good correlation displayed with these two parameters. The light absorption coefficient of non-living particulate matter (aNLPM) was found to correlate generally with POC, but with varying coefficients between sites. In the Baltic Sea, variations of the organic-rich TSM (36% in POC) do not determine significant variations of aNLPM as in the other sites where TSM is dominated by inorganic matter (e.g. in the North Sea and in the English Channel).