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Dissolved organic matter (DOM) is conventionally considered to be all organic molecules large enough to pass through a filter with 0.2 ým porosity. It represents a significant component in the carbon cycle (Jackson, 1993, Yananaka and Tajika, 1997). It strongly influences the quality of coastal or delta waters (Klemas et al. 1990) and the annual contribution of carbon to the oceans by rivers has been estimated at 2.15 x 1014 g. of C. a year (Meybek, 1982). In remote-controlled surveys CDOM is that part of DOM able to absorb visible light (350-750 mm). It may seem surprising but CDOM represents that component of water which mostly absorbs light in the blue part of the spectrum. Some examples: In the Upper Adriatic absorption by CDOM (aCDOM) is on average 6 times more than that of waste and pigments (Grossi et al., 1998). In the Baltic Sea (Gulf of Gdansk) aCDOM represents more than 80% of the total absorption (Ferrari and Dowell, 1998, fig. 1). These readings give the measure of how much aCDOM can influence the calculation by remote-controlled surveys of the chlorophyll which absorbs light in the same spectral area in non-oceanic waters (Tassan, 1988, Ferrari and Tassan, 1992, Carder et al., 1989).

Fortunately, chlorophyll has an absorption peak in red where aCDOM is nil or negligible. This has allowed new algorithms able to separate the contribution of CDOM from that of planktonic pigments to be studied and planned using new generation sensors (SeaWiFS, OCTS, MOS, MODIS and MERIS) and on site measuring campaigns. .

Additional information

Bibliographic Reference: Article:Telerilevamento ed Ecologia Marina dal Problema All'applicazione, pp:227-247
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