Effects of temperature on growth, associated bacterial communities, and fatty acid profiles of a Korean isolate of Scrippsiella acuminata (Dinophyceae)

Temperature is an important environmental factor influencing the growth and physical responses of dinoflagellates. However, information on temperature-dependent changes in associated bacterial communities and fatty acid profiles of Scrippsiella acuminata remains limited. To investigate the effects of temperature on the growth, associated bacterial communities, and fatty acid profiles of a Korean isolate of Scrippsiella acuminata , cultures were examined at 15, 20, and 25 °C. The growth rate of S. acuminata was significantly lower at 15 °C than at 20 °C and 25 °C, while bacterial abundance increased concurrently with algal growth across all temperature treatments. Temperature effects on bacterial alpha diversity were limited and varied among diversity metrics. In contrast, taxonomic composition showed significant differences in specific dominant genera. In particle-associated bacteria (PAB), Candidatus Phaeomarinobacter was significantly more abundant at 25 °C than at 15 °C and 20 °C, whereas in free-living bacteria (FLB), Marivita was significantly more abundant at 15 °C than at 25 °C. Oceanicaulis was abundant in both bacterial fractions but showed no significant differences among temperature treatments. Total fatty acid content in S. acuminata cultures did not differ significantly among temperatures. C16:0, C20:0, C18:1, and DHA showed no significant differences among temperature treatments, whereas EPA content was significantly higher at 25 °C than at 15 °C and 20 °C. These findings indicate that temperature strongly affected the growth of S. acuminata , whereas responses of associated bacterial communities and fatty acid profiles were more selective, occurring at the level of specific bacterial taxa and fatty acids.