The work presents the underpinning for using of the spectral approach for assessment of primary productivity indicators based on remote sensing data. Existing information has been analysed. Problems, which should be solved for practical implementation of the spectral model of primary production in the Black Sea based on satellite data, have been identified. It has been shown that application of the regional algorithms for the assessment of the Black Sea primary productivity indicators on the basis of satellite data has improved the accuracy of model assessment of phytoplankton pigment concentration in the sea. Obtained for the last decade data of bio-optical water properties and photo-physiological characteristics of phytoplankton in the Black Sea allow to switch to the new level of regional models, which take into account not only amount, but also the spectral composition of radiation available for photosynthesis. The spectral model takes into account differences in phytoplankton light absorption efficiency between seasons as well as between euphotic zone layers separated by thermocline. Conceptually, this model is more realistic, and could be used not only for operational monitoring of the Black Sea waters, but also for development of predictive models for the sea ecosystem changes.
Climate affects the characteristics of the Southern Ocean ecosystem, including bio-optical properties. Remote sensing is a suitable approach for monitoring a rapidly changing ecosystem. Correct remote assessment can be implemented based on a regional satellite algorithm, which requires parameterization of light absorption by all optically active components. The aim of this study is to analyse variability in total chlorophyll a concentration (TChl-a), light absorption by phytoplankton, non-algal particles (NAP), coloured dissolved organic matter (CDOM), and coloured detrital matter (CDM = CDOM+NAP), to parameterize absorption by all components. Bio-optical properties were measured in the austral summer of 2020 according to NASA Protocols (2018). High variability (1–2 orders of magnitude) in TChl-a, absorption of phytoplankton, NAP, CDOM, and CDM was revealed. High variability in both CDOM absorption (uncorrelated with TChl-a) and CDOM share in total non-water absorption, resulting in a shift from phytoplankton to CDOM dominance, caused approximately twofold chlorophyll underestimation by global bio-optical algorithms. The light absorption of phytoplankton (for the visible domain in 1 nm steps), NAP, CDOM, and CDM were parametrized. Relationships between the spectral slope coefficient (SCDOM/SCDM) and CDOM (CDM) absorption were revealed. These results can be useful for the development of regional algorithms for Chl-a, CDM, and CDOM monitoring in the Southern Ocean.
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