EARSeL eProceedings Vol. 3, No. 2, 261-275, 2004

Abstract
Biogeochemical provinces vary due to physical and chemical changes in the marine environment. Water-leaving radiance has been used to investigate naturally occurring pigments in phytoplankton communities. Whereas in the open, ocean colour can easily be converted to total pigment concentrations, there are shortcomings in determining photosynthetic pigments in eutrophied coastal regimes. This is based on the fact that water-leaving radiance in coastal regions varies in relation to the changing composition of the main contributor to the water-leaving radiance.

In order to observe the spectral response of water over a wide range of chlorophyll and accessory pigments, a test site was selected that supports high plankton blooming through nutrient transport from a waste water treatment facility to the marine ecosystem. Several carotenoids were found to correlate with the spectral region where chlorophyll is shown in the second absorption band. As the same pigments are also correlated with each other, this correlation can be regarded as an artifact.

The first derivative of reflectance in the near 690 nm region was investigated in this study. The results showed that measurements of spectral reflectance ratios for water-leaving radiance in the spectral region of the second absorption band of chlorophyll could be effective for empirically derived semi-quantitative relationships for concentrations of chlorophyll and related pigments. Measurements with MODIS demonstrate that the ratio 667/678 may be useful as an indicator for high chlorophyll concentrations close to the surface and can be used to describe the upper layer of the euphotic zone. The ratio technique was applied for separating bio-geochemical provinces when compared with chlorophyll measurements based on the first absorption band of chlorophyll. Preliminary results are presented for several oceanic regions using a clustering approach to relate chlorophyll data and the ratio technique.

ISSN 1729-3782