A comparison of biological responses of benthic and planktic foraminifera to alteration in seawater CO2 and pH

<p>The ocean absorbs large amounts of CO<sub>2</sub> emitted from human activities, which lead a decrease in seawater pH and has potential damage to marine calcareous organisms. Foraminifera is one of the most important marine calcareous organisms in the ocean, while the biological response of benthic and planktic foraminifera to seawater CO<sub>2</sub> increase and pH decline is still unknown. In this study, a comparison of the biological response of benthic and planktic foraminifera to seawater CO<sub>2</sub> increase and pH decline was studied through series of culture experiments. Our experimental results showed the increase of CO<sub>2 </sub>or decrease of seawater pH adversely affected the biological processes of both benthic and planktic foraminifera may resulted in declining community diversity, weaker predation, slower growth, lighter shells and more deformities. In addition, we found microalgae that lives with planktic foraminifera are also killed under low pH conditions. Our study provided experimental data for understanding the biological response of calcareous micro-organisms to ocean acidification. Our results indicated that ongoing ocean acidification may retard the growth and calcification by changing their biological processes. This would have profound effects (e.g., reduced carbonate deposition and predation) on the carbon cycle and energy flow in the marine food web (This research received financial supports from the following projects: National Natural Science Foundation of China (Grant No, 41976058); The Strategic Priority Research Program of the Chinese Academy of Sciences (XDB42000000).</p>