Ecophysiology of the kleptoplastidic dinoflagellate Shimiella gracilenta: II. Effects of temperature and global warming

Abstract

Water temperature affects plankton survival and growth. The dinoflagellate Shimiella gracilenta survives using the plastids of ingested prey, indicating kleptoplastidy. However, studies on the effects of water temperature on kleptoplastidic dinoflagellates are lacking. We explored the growth and ingestion rates of S. gracilenta as a function of water temperature. Furthermore, using data on its spatiotemporal distribution in Korean coastal waters during 2015-2018, we predicted its distribution under elevated temperature conditions of +2, +4, and +6 degrees C. Growth rates of S. gracilenta with and without Teleaulax amphioxeia prey as well as ingestion rates were significantly affected by water temperature. Growth rates of S. gracilenta with and without prey were positive or zero at 5-25 degrees C but were negative at >= 30 degrees C. The maximum growth rate of S. gracilenta with T. amphioxeia was 0.85 d(-1), achieved at 25 degrees C, and 0.21 d(-1) at 20 degrees C without prey. The ingestion rate of S. gracilenta on T. amphioxeia at 25 degrees C (0.05 ng C predator(-1) d(-1)) was greater than that at 20 degrees C (0.04 ng C predator(-1) d(-1)). Thus, feeding may shift the optimal temperature for the maximum growth rate of S. gracilenta from 20 to 25 degrees C. In spring and winter, the distributions of S. gracilenta under elevated temperature conditions were predicted not to differ from those during 2015-2018. However, S. gracilenta was predicted not to survive at some additional stations under elevated temperature conditions of +2, +4, and +6 degrees C in summer or under elevated temperature conditions of +6 degrees C in autumn. Therefore, global warming may affect the distribution of S. gracilenta.