ScholarWorks@성균관대학교

초록

Marine dinoflagellates are increasingly exposed to concurrent ocean warming and eutrophication; however, their responses to multiple concurrent stressors remain inadequately understood. Here, we investigated the individual and combined effects of elevated temperature (26 degrees C vs. 22 degrees C) and a high nitrogen-to-phosphorus ratio (180:1) on the harmful algal bloom-causing dinoflagellate Karenia mikimotoi during a 30-day exposure experiment. Elevated temperature and high N:P ratio, individually and in combination, significantly increased growth rate by 16-24 % relative to the control, while chlorophyll a (Chl a) content decreased by 22-29 %. Cellular particulate organic nitrogen (PON) content declined by 21-22 % under elevated temperature alone and in combination with a high N:P ratio, whereas particulate organic carbon (POC) content remained unchanged across all treatments. Interaction analyses revealed antagonistic effects of elevated temperature and high N:P ratio on growth rate, Chl a, and PON contents. Transcriptomic analyses showed that elevated temperature primarily upregulated genes associated with energy production and lipid biosynthesis, whereas a high N:P ratio enhanced the expression of genes involved in nitrogen assimilation and urea cycle-related pathways. Under combined stress, gene expression patterns indicated a transcriptionally inferred shift in energy allocation toward soluble sugar and lipid metabolism, accompanied by downregulation of urea cycle-related genes, suggesting a trade-off between energy conservation and nitrogen utilization. These results highlight the importance of antagonistic interactions between warming and nutrient imbalance in shaping the physiological and molecular responses of dinoflagellates, with implications for predicting harmful algal bloom dynamics under future ocean conditions.

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