Effect of Light, Temperature, and Nutrient Deficiency on Structural and Functional Characteristics of the Coccolithophore Emiliania huxleyi (Prymnesiophyceae)

Abstract A clonal culture of the coccolithophore Emiliania huxleyi was isolated from the Black Sea plankton in February, 2023. Using scanning electron microscopy method, its species identification was performed. It was established that it belongs to the type A. The optimal temperature for the development of this culture (20°C) was detected. A temperature coefficient (Q 10 ) was 3.36 for the temperature range 5–15°C, 2.75 for 10–20°C. The effect of light on the structural and functional parameters of this species was studied. The specific growth rate reached a maximum (1.37 day –1 ) at the intensity of 157 μE/(m 2 s), then decreased as a result of light inhibition. The relative content of chlorophyll a per cell and dry weight decreased by 3–5 times as the light intensity increased from 8.5 to 425 μE/(m 2 s). A transfer of E. huxleyi cells (that have a maximal intracellular pool of nutrients) to seawater depleted of nutrients caused a decrease in their population growth and efficiency of photosystem II, as well as an increase in the cell volume and surface area. The sensitivity of photosystem II to phosphorus deficiency was higher than to nitrogen deficiency. Due to the intracellular pool of nutrients, this species of algae performed 1.43–1.77 cell divisions.