Chlorophyll Measurements in the Presence of Suspended Sediment Using Broad Band Spectral Sensors Aboard Satellites

Abstract

ABSTRACT Concentrations of chlorophyll-a in waters with high average annual concentrations of suspended sediment were measured in three lakes and compared with broad band Landsat MSS satellite digital data for 104 dates between December 1976 and August 1988. Concentrations of chlorophyll-a ranged from 0.3 to 211 mg·m−3 for 452 measurements. Concentrations of suspended sediment ranged from 1 to 867 mg·l−1 in the same samples. In general, chlorophyll-a concentrations were inversely related to suspended sediment concentrations. Radiance and reflectance calculated from the four MSS bands increased as a function of increasing concentrations of suspended sediment. Radiance and reflectance were inversely related to the concentration of chlorophyll-a, but the relationships were not statistically significant. This study indicated that the measurement of chlorophyll-a with broad band (100 nanometer) MSS data in waters dominated by suspended sediments is not effective since the detection of the increased absorption or reflectance of radiation due to chlorophyll-a is masked by the spectral reflectance due to suspended sediments. In order to quantitatively determine chlorophyll by remote sensing in systems dominated by suspended sediment high spectral resolution information (10 to 15 nm band widths) at approximately 675 and 705 nanometers (nm) will be required.