Ecophysiology of Extremophilic Diatom Alga Nitzschia cf. thermaloides from Mud Volcanoes of Crimea

The diatom alga Nitzschia cf. thermaloides can be found in large numbers in puddles and lakes in the places where mud volcanoes function in the area of the Bulganak mud volcano field (eastern Crimea). Environmental conditions in such reservoirs are extreme: salinity is from 18 to ≥70‰, insolation is extremely high, and ultraviolet radiation is very strong. The growth rate and the intensity of sexual reproduction of N. cf. thermaloides at different salinity and illumination levels have been studied in laboratory conditions. We have determined the limits of halotolerance and the optima of salinity and illumination for growth and sexual reproduction of the alga, capable of vegetative reproduction in an environment with salinity from 0 to 220‰. The range for sexual reproduction is narrower, from 6 to 54‰. The salinity of 22–25‰ and illumination of about 1.5 klx are optimal for both vegetative and sexual reproduction of N. cf. thermaloides.