Reflectance spectra of polluted marine waters in Haifa Bay, Southeastern Mediterranean: Features and application for remote estimation of chlorophyll concentration

Chlorophyll distribution in Haifa Bay was estimated during a period of very high chlorophyll concentrations (up to 70 mg/m³) using remotely sensed data. Radiometric measurements with spectral resolution of 2 nm in the range from 400 nm to 850 nm were taken simultaneously with a Secchi disk transparency and samples for determination of chlorophyll concentration and turbidity. High spectral resolution data were used for the selection of the most suitable spectral bands for remote estimating of chlorophyll concentration. The magnitude and position of the peak near 700 nm were highly correlated with chlorophyll concentration. The reflectance height at 690 nm above the baseline from 670 nm to 850 nm and area above the baseline were used as sensitive indicators of chlorophyll concentration. The best model enabled estimation of chlorophyll concentration with an error of less than 4.3 mg/m³. For the purpose of chlorophyll mapping in Haifa Bay, the use of three relatively narrow spectral bands was sufficient. Radiometric data were also used to simulate radiances in the channels of Thematic Mapper (TM) Landsat and to find the algorithm for chlorophyll assessment. The ratios TM3/TM1 and (TM2-TM3)/TM1 were used, permitting chlorophyll estimation with an error of less than 8 mg/m³.