The Effect of Viral Infection on Coccolithophorid Emiliania huxleyi upon Different Levels of Biogenic Elements in the Medium

Coccolithophorid Emiliania huxleyi was isolated to clonal culture from plankton of coastal waters of the Black Sea in February, 2023. Algal virus strain EhV-SS2 affecting this algal species was isolated from coastal waters in May, 2023. By means of scanning electron microscopy, it was shown that viral particles were 124–174 nm in diameter with an icosahedral symmetry. Supercapsid was detected in this strain and its titer was determined (2.5 × 10⁵ virions/mL). The effect of algal virus on E. huxleyi growth and efficiency of PS II (F_v/F_m) at different levels of biogenic elements in the medium was investigated. Throughout the latent period of algal virus (0–101 h), we observed a decrease in the F_v/F_m ratio in the algae as compared with control values. Within time interval from 101 to 168 h, first cells lysed by the virus were revealed in the culture by means of light and scanning electron microscopy. Over the period from 168 to 264 h, lysis intensified and its rate on full f/2 medium was five times greater than in the case of nitrogen or phosphorus deficit. The rate of cell lysis on seawater lacking nutrient elements was two times lower than on the full medium. By the end of the experiment (in 264 h), infected culture displayed functionally active cells sheeted with coccoliths and without them. The percentage of the latter on f/2 medium was 95%, whereas in the case of nitrogen and phosphorus deficit their proportion was small.