Marine constituents detected by a SeaWiFS algorithm in the south- eastern Mediterranean

Remote detection of water-leaving radiance is quantitatively related to three marine constituents that exist in the water column: chlorophyll (Chl); suspended matter (SM) such as sediments; and coloured dissolved organic matter (CDOM), also known as Gelbstoff (Bukata et al. 1995). The variation of the volume reflectance of these constituents is rather complicated, as illustrated in figure 1. Volume reflectance of water with minimum Chl concentrations is relatively high in the blue spectral region (400–500 nm) and minimal in the red region (600–700 nm). Conversely, high Chl concentrations lower the volume reflectance in the blue region and heighten it in the red region. The null point of these vertical shifts is located at around 500 nm. Increasing concentrations of CDOM result in a significant decrease of the volume reflectance in the blue region with almost no effect in the red region. As for the SM, increasing concentrations produce a considerable increase of the volume reflectance in the red region with minimal effect in the blue region. Therefore, the detection of slight changes in Chl content through remote sensing is challenging, especially at the higher Chl concentrations commonly found in coasta