Воздействие температуры на рост двух видов Pseudo-nitzschiah. Peragallo (bacillariophyta) в лабораторных культурах, изолированных из Японского моря

Abstract

The diatoms belonging to the genus Pseudo-nitzschia H. Peragallo, 1900, known as producers of the neurotoxic domoic acid, regularly cause algal blooms in the Russian Far Eastern seas. Temperature is an important factor influencing diatom blooms; however, its impact on the growth of this group of microalgae from the Sea of Japan has not been sufficiently studied. In this regard, the growth characteristics of two species of diatoms were studied in laboratory culture within the temperature range of 5 to 20 °C using direct counting in a Najott chamber. Cell density, growth rates, and generation time were evaluated. It was found that the maximum average density of P. fraudulenta reached 219,000 cellsl^-1 on the 16th day of the experiment at 18 °C. For this species at 18 °C, the growth rate (0.11-0.16 divisionsday^-1) remained relatively high and the generation time (4.4-6.7 days)was relatively low for most of the experiment. The maximum mean density of P. hasleana (49,583 cellsl^-1) was recorded on the 16th day of the experiment at 17 °C. For this species, high growth rate (0.2-0.92) and low generation time (0.8-3.6 divisionsday^-1) were recorded at 17 °C from day 2 to day 10 of the experiment. The average densities of P. fraudulenta and P. hasleana at 17 °C and 18 °C, respectively were statistically significantly higher than at the other temperatures studied. It was found that when P. fraudulenta and P. hasleana clones were grown at temperatures of 10, 16 and 18 °C and 14, 17 and 20 °C, respectively, the cells remained in a viable state and continued to divide. When the cultivation temperature of P. fraudulenta and P. hasleana was lowered to 5 °C and 7 °C, respectively, division slowed down dramatically and cell density was statistically significantly lower than at higher temperatures.It was found that the range of tolerant temperature during cultivation of P. fraudulenta and P. hasleana varied from 10 to 18 °C and 14 to 17 °C, respectively. The revealed lower temperature tolerance limits found for the two species during cultivation (10 and 14 °C) corresponded to the temperature conditions under which blooms of P. fraudulenta and P. hasleana were observed in the natural environment (Peter the Great Bay, the Sea of Japan): 6-16 °C and 10-16 °C, respectively. The study demonstrated the broad adaptive potential of the studied species to temperature changes.

Keywords: Pseudo-nitzschia fraudulenta, Pseudo-nitzschia hasleana, laboratory cultivation, temperature, Sea of Japan