Physiological Mechanism of Dinoflagellate Survival under a Biogenic Limitation
2021
Stelmakh, L. V. | Mansurova, I. M.
The physiological mechanism of the long-term survival of dinoflagellates under a biogenic limitation has been studied using the cultures of three common species from the Black Sea—Prorocentrum cordatum, Prorocentrum micans, and Gyrodinium fissum—as an example. The transfer of P. cordatum and G. fissum cells, which have a maximum intracellular pool of nutrients, to seawater depleted in nutrients decreases their specific growth rate and chlorophyll a content per cell. Due to the intracellular pool of nutrients, P. cordatum performs 3.3 cell divisions in 9 days and G. fissum performs 2.3 cell divisions in 4 days. After the exhaustion of the intracellular reserves of nutrients in the culture of G. fissum for 16 days, the growth of its cells ceases and the specific content of chlorophyll a, as well as the efficiency of the photosystem 2, decreases. In the P. micans culture, which is under the conditions of the most severe biogenic limitation throughout the 20-day experiment, against the background of an almost constant number of cells, an alternation of low positive and negative values of the specific growth rate is observed, as well as a low content of chlorophyll a per cell. However, the efficiency of photosystem 2 remains at a sufficiently high level (0.27–0.41) and exceeds the control values most of the time. This study reveals a high degree of heterogeneity of the functional activity of this species cells and the death of some of them under biogenic stress. The survival of P. micans under biogenic stress is probably ensured by the nutrients that enter the water during the death of the least viable part of its cells and serves as a source of organic matters for the physiologically active cells of microalgae.
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