Phytoplankton photosynthetic parameters in waters near the Kamchatka Peninsula in August-September 2023

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  • Authors: T. V. Efimova1,2, T. Ya. Churilova1,2, N. A. Moiseeva1, E. Yu. Skorokhod1,2, P. A. Salyuk3, A. V. Yatsuk4
  • Affiliations:
    1. A. O. Kovalevsky Institute of Biology of the Southern Seas of Russian Academy of Sciences, Sevastopol, Russian Federation
    2. Laboratory of Ecology and Evolutionary Biology of Aquatic Organisms, Institute of World Ocean, Far Eastern Federal University, Vladivostok, Russian Federation
    3. V.I. Ilichev Pacific Oceanological Institute Far Eastern Branch Russian Academy of Sciences, Vladivostok, Russian Federation
    4. Sirius University of Science and Technology, Sirius, Russian Federation
  • Keywords: chlorophyll fluorescence, photoacclimation, rapid light curve, quantum yield of photosynthesis, the Pacific Ocean, the Sea of Okhotsk

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Abstract

The climate change and increasing anthropogenic pressure affect the aquatic ecosystems. State and productivity of pelagic ecosystems are largely determined by photosynthetic capacity of phytoplankton. The aim of this study was to analyze the variability of phytoplankton photosynthetic parameters (quantum yield of photosynthesis (ϕ), which characterizes efficiency of absorbed light quanta utility in photosynthesis, its potential capacity (ϕmax) and light-saturation coefficient (Ik)) related to light conditions varied due to different ratio between the upper mixed layer (UML) and euphotic zone. The study was carried out based on data obtained in the Pacific Ocean and the Sea of Okhotsk during the 23/4th cruise of the R/V “Professor Multanovskiy” in August-September 2023. The ϕmax and Ik were calculated based on measurements of rapid light-response curves of variable fluorescence. It was found out that variability in the photosynthetic parameters was mainly determined by phytoplankton physiological acclimation to light. Acclimation to light, which differed between the UML and the deeper layer of the euphotic zone, resulted in distinct light-response patterns of relative electron transport rate curves. The Ik values were directly related to light intensity. Nonetheless, the values of ϕmax were inversely related to light intensity, but to a larger extent compared to the Ik. As a result, ϕ, which depends on the Ik and ϕmax, decreased with increasing light intensity. A tight relationship between the values of ϕ and light intensity (r = 0.97) was revealed (p < 0.0001) and described by an exponential function. This analysis showed peculiarities of the light forcing variability in photosynthetic parameters. The revealed dependences of the Ik, ϕmax and ϕ on light intensity can be used for express assessment of their values based on light, which is necessary for assessment of primary production using spectral approach.

Keywords: chlorophyll fluorescence, photoacclimation, rapid light curve, quantum yield of photosynthesis, the Pacific Ocean, the Sea of Okhotsk

Authors

T. V. Efimova
A. O. Kovalevsky Institute of Biology of the Southern Seas of Russian Academy of Sciences, Sevastopol, Russian Federation / Laboratory of Ecology and Evolutionary Biology of Aquatic Organisms, Institute of World Ocean, Far Eastern Federal University, Vladivostok, Russian Federation
T. Ya. Churilova
A. O. Kovalevsky Institute of Biology of the Southern Seas of Russian Academy of Sciences, Sevastopol, Russian Federation / Laboratory of Ecology and Evolutionary Biology of Aquatic Organisms, Institute of World Ocean, Far Eastern Federal University, Vladivostok, Russian Federation
N. A. Moiseeva
A. O. Kovalevsky Institute of Biology of the Southern Seas of Russian Academy of Sciences, Sevastopol, Russian Federation
E. Yu. Skorokhod
A. O. Kovalevsky Institute of Biology of the Southern Seas of Russian Academy of Sciences, Sevastopol, Russian Federation / Laboratory of Ecology and Evolutionary Biology of Aquatic Organisms, Institute of World Ocean, Far Eastern Federal University, Vladivostok, Russian Federation
P. A. Salyuk
V.I. Ilichev Pacific Oceanological Institute Far Eastern Branch Russian Academy of Sciences, Vladivostok, Russian Federation
A. V. Yatsuk
Sirius University of Science and Technology, Sirius, Russian Federation