Effects of temperature on the autotrophic and mixotrophic growth rates of the dinoflagellate Biecheleria cincta and its spatiotemporal distributions under current temperature and global warming conditions

Water temperature is a major parameter affecting the growth and distribution of mixotrophic dinoflagellates. To predict the distribution of a mixotrophic dinoflagellate during a global warming period, the dinoflagellate growth rate as a function of water temperature and distribution under current temperature conditions should be explored. The autotrophic and mixotrophic growth and ingestion rates of Biecheleria cincta BCSH1005 feeding on the suitable prey raphidophyte Heterosigma akashiwo at 5-35 degrees C were determined. Also, the spatiotemporal distributions of B. cincta in Korean coastal waters collected from 27 stations 16 times in 2015-2018 were investigated using the quantitative real-time polymerase chain reaction. The distributions of B. cincta under + 2, + 4, and + 6 degrees C water temperature conditions were predicted using the results of field observations. At all tested water temperatures, B. cincta did not grow autotrophically. However, B. cincta grew mixotrophically by feeding on H. akashiwo at 15-25 degrees C, with a maximum growth rate of 0.26 day-1 at 25 degrees C, but B. cincta did not grow at lower or higher temperatures. In 2015-2018, B. cincta was detected at 3, 8, 5, and 1 stations in spring, summer, autumn, and winter, respectively. Under the + 2, + 4, and + 6 degrees C conditions, the numbers of stations at which B. cincta was present were predicted to be 6, 5, and 3, respectively, in summer and 5, 5, and 3, respectively, in autumn. However, no change in the number of stations in spring and winter was predicted. Therefore, trophic mode and water temperature may affect the survival and distribution of B. cincta.