Fluorescence of Chlorophyll a during Seasonal Water Stratification in the Black Sea

Abstract

Purpose. At present the express method of estimating the chlorophyll a concentration by its fluorescence is widely spread. The applied in calculations coupling coefficient between these two values is assumed to be constant (in time and space); but it does not correspond to reality. Therefore, the basic purpose of the paper consists in studying dependence of fluorescence on the chlorophyll a concentration in the deep part of the Black Sea in a warm period when seasonal water stratification is observed.

Methods and Results. Relation between the light absorption by the phytoplankton pigments, and the chlorophyll a concentration and fluorescence is investigated. It is shown that the ratio between the chlorophyll a concentration and fluorescence was different in the quasi-isolated layers during the seasonal water stratification. Revealed is the vertical heterogeneity of fluorescence normalized for the chlorophyll a concentration in the euphotic layer. It is conditioned by change of the phytoplankton ability to absorb light quanta at the wavelength ~455 nm (fluorescence excitation) calculated for a unit of the chlorophyll a content. Comparison of the specific values of fluorescence and light absorption index on the wavelength ~455 nm showed their strong mutual correlation that testifies to insignificant variation of the values of the fluorescence quantum yield within the photosynthesis zone.

Conclusions. The obtained dependences between the chlorophyll a concentration and fluorescence can be used to specify the algorithms applied at present for reconstructing the chlorophyll a concentration profiles based on the data of either the fluorescence submerged probes or the drifting floats of the international project Biogeochemical Argo.

Keywords

chlorophyll a, fluorescence, light absorption, quantum yield, phytoplankton, the Black Sea.

Acknowledgements

The research is carried out according to the state order No. АААА-А18-118020790229-7, theme “Study of Spatial-Temporal Organization of Aquatic and Land Ecosystems Aimed at Development of Operational Monitoring System based on the Remote Sensing Data and GIS Technologies” No. АААА-А19-119061190081-9 and theme “Comprehensive Studies of the Current State of the Ecosystem of the Atlantic Sector of the Antarctic” as well as under the partial RFBR support, grants No. 17-05-00113 and 18-45-920070. The authors are very thankful to the expedition head A. S. Mikaelyan and to the group of hydrological research, S. A. Shutov and P. O. Shapovalov, for their arrangement of research.

Original Russian Text © The Authors, 2019,
published in MORSKOY GIDROFIZICHESKIY ZHURNAL, Vol. 35, Iss. 5, pp. 481–495 (2019)

For citation

Moiseeva, N.A., Churilova, T.Ya., Efimova, T.V., Krivenko, O.V. and Matorin, D.N., 2019. Fluorescence of Chlorophyll a during Seasonal Water Stratification in the Black Sea. Physical Oceanography, [e-journal] 26(5), pp. 425-437. doi:10.22449/1573-160X-2019-5-425-437

DOI

10.22449/1573-160X-2019-5-425-437

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