Spectral variations of the remote sensing reflectance during coccolithophore blooms in the Western Black Sea

[摘要] Among the many calcifying marine organisms, coccolithophores are the major producer of particulate inorganic carbon (PIC). Calcium carbonate plates covering coccolithophores, called coccoliths and released during blooms, are responsible for a large increase of the water reflectance. Aiming at investigating the spectral features of the remote sensing reflectance R-RS(lambda) of marine waters during coccolithophore blooms, this study exploits the radiometric data of Ocean Color sites of the Aerosol Robotic Network (AERONET-OC) in the Western Black Sea (Galata and Gloria/Section-7) by focusing on bloom events that occurred in 2017 and 2020. The analysis, besides showing elevated R-RS(lambda) in the blue-green spectral region in the presence of coccoliths, confirms a shift toward the blue of the R-RS(lambda) spectra as the bloom declines and coccoliths accumulate at the surface. Results also document a decreased capability of determining the bloom state in the presence of optically complex waters such as those associated with river runoff. Finally, the comparison of satellite versus AERONET-OC radiometric data for the extreme conditions created by the presence of coccolithophores, indicates agreements between R-RS(lambda) not significantly different from those previously determined for various satellite data products in the absence of appreciable concentrations of coccoliths.

[发布日期] 2021-10-01

[关键词] Remote sensing;Ocean color;Coccolithophores;Phytoplankton;Radiometry;Satellite;Remote sensing reflectance