Nature of the peak near 700-nm on the radiance spectra and its application for remote estimation of phytoplankton pigments in inland waters

To investigate the nature of a peak near 700 nm on the reflectance spectrum of water, simultaneous measurements of the reflectance spectra in the region of 400 to 750 nm and relevant water quality constituent concentrations (phytoplankton chlorophyll-a, dissolved organic matter, and suspended matter) were carried out. A shift of the peak position from about 680 nm up to 715 nm and an increase of the peak magnitude, when chlorophyll concentration increased from 3 up to 100 μg/l, were observed. The relationships of the magnitude and position of the peak to chlorophyll-a, obtained in the first data set, were applied to several independent data sets. These data sets cover various trophic states of water bodies, all seasons, and a variety of climatic regimes. Comparison of predicted and measured pigment concentrations shows that the peak parameters can be used as precise indicators and predictors for phytoplankton concentration. It contributes significantly to the increase in the accuracy of remote estimation of pigment concentration in productive inland waters.