Effect of ocean warming on pigment and photosynthetic carbon fixation of plankton assemblage in Pingtan Island of Southeast China.

Temperature plays an important role in affecting the physiological traits of marine plankton. In this study, we conducted an outdoor incubation experiment to investigate the effects of elevated temperature on Chl a, photosynthetic carbon fixation and the composition of plankton communities in the surface seawater around Pingtan Island, the northwest Taiwan Strait in Autumn 2022. After 3-4 days of incubation, elevated temperature (1-4 °C higher than ambient temperature) led to a decrease in Chl a concentration across all three stations, did not result in significant increases in the particulate organic carbon (POC) and nitrogen (PON) concentrations in seawater with high nitrate concentrations, whereas increased POC and PON concentrations in nitrate-limited seawater. These findings suggest that the effect of temperature on the POC and PON contents of plankton is affected by the availability of nitrate. Diatoms were the dominant phytoplankton group in all three stations. Our results indicate that ocean warming has a potential to increase the POC contents of marine plankton per volume of seawater, which may increase the ability of phytoplankton to absorb atmospheric CO and to alleviate global warming.