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General Session 3: Biological oceanography & global change |
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Separate effects of pCO2 and pH on the diatoms Phaeodactylum tricornutum and Thalassiosira pseudonana
GS3-49-S
Xi Su* , State Key Laboratory of Marine Environmental Science, Xiamen University
Haizheng Hong, State Key Laboratory of Marine Environmental Science, Xiamen University
Dalin Shi, State Key Laboratory of Marine Environmental Science, Xiamen University
Presenter Email: iisushi@stu.xmu.edu.cn
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| Oceans act as a sink for increasing anthropogenic CO2. This process changes seawater carbonate chemistry, resulting in an increase in partial pressure of CO2 (pCO2) and a decrease in pH, which are commonly referred to as ocean acidification. Diatoms contribute about 40ге of marine primary production and play a key role in carbon export to deep seawater. Previous studies have shown stimulative, neutral or inhibitory effects of elevated seawater acidification on the growth of diatoms. However, how diatoms respond to the change in pH and pCO2 individually basically remains unknown. Here we examined separate effects of pCO2 and pH on diatoms, using synthetic ocean water (SOW) as the culture media in which pCO2 and pH were varied independently by adjusting the alkalinity and dissolved inorganic carbon concentration. Growth, chlorophyll fluorescence, carbon metabolism, nitrogen assimilation, elemental and biochemical compositions of the diatoms Phaeodactylum tricornutum and Thalassiosira pseudonana were systematically assessed. Our preliminary results showed that the stimulative effect of ocean acidification on the growth of P. tricornutum was largely due to the decrease in respiration rate at elevated pCO2. Although ocean acidification also reduced the respiration rate in T. pseudonana, lower pH reduced the gross photosynthetic rate in the mean time, consequently resulting in neutral net effect. |
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