Development of the satellite bio-optical algorithm for the shelf waters along the southern Kamchatka Peninsula: effect of optically active components variability on the spectral remote sensing reflectance

A data set including in situ absorption of particulate and dissolved coloured organic matter, absorption of phytoplankton and chlorophyll-a concentration was measured during the research cruise on board R/V “Professor Multanovsky” on August-September, 2023 in shelf waters of the south Kamchatka Peninsula. In order to adjust the existing semi-analytical algorithm to the optically complex waters, the regional parameterization of in-water optically active components absorption was used. Based on in situ bio-optical properties the reflectance spectra were modeled and used for the algorithm testing. The algorithm allows to separate the absorption of phytoplankton and colored detrital matter using the separate spectral sites for their calculation. The total non-water absorption was retrieved with high accuracy, while phytoplankton absorption (chlorophyll-a concentration) was overestimated on average by 35%, and CDM absorption was underestimated on average by 32%. Accuracy of their retrievals allows the application of the algorithm for ecological monitoring. An analysis showed that the reflectance spectral shape is strictly determined by the total non-water absorption. The high variability of ratios between optically active components leads to weak connection between reflectance spectral shape and specific optical components. Further refining of the semi-analytical algorithm consists in a selection of more suitable spectral sites and switching between them based on the contributions of components to the total absorption. • Optical complexity of shelf water near southern Kamchatka Peninsula. • Variability of bio-optical properties and reflectance spectral features. • Assimilation of regional bio-optical properties in semi-analytical algorithm. • Algorithm provides correct assessments in optically complex waters.