1668 / 2019-08-26 11:22:18

Effect of ocean acidification on picocyanobacteria in the South China Sea under the influence of nutrient availability

6、海洋地球科学 > 专题8：热带海洋多尺度气候变化及其对全球气候的响应和影响

Effect of ocean acidification on picocyanobacteria in the South China Sea under the influence of nutrient availability
Rongbo Dai, Zuozhu Wen, Wenfang Lin, Jian Pang, Haizheng Hong, Dalin Shi

There is a growing consensus that ocean acidification (OA) caused by increasing atmospheric CO2 concentration will lead to a variety of effects on marine phytoplankton. However, little is known about how natural picocyanobacteria populations, which contribute significantly to the ocean primary production, will respond to OA. We conducted onboard incubation experiments with surface waters at three stations in the South China Sea where phytoplankton community was dominated by the picocyanobacteria Prochlorococcus and Synechococcus. In addition, nitrogen and/or phosphorus were added to examine the influence of nutrient availability on acidification effects. Our results revealed that the phytoplankton community was dominated by picocyanobacteria (72-83%), and after a 3-day incubation no response of Chl a to OA was observed. Under acidified conditions, the proportion of Synechococcus increased by 2-19%, whereas that of Prochlorococcus remained nearly unchanged. Similarity, flow cytometry analyses also showed that the abundance of Synechococcus increased by 6-64% under OA, while no response of Prochlorococcus was observed. Therefore our results suggested that Synechococcus may benefit from OA as compared to Prochlorococcus. Meanwhile, we found that only when nitrogen and phosphorus added simultaneously the grow of Synechococcus was promoted and showed positive response to OA. In contrast, the growth of Prochlorococcus was limited by nitrogen only. In addition, the carbon fixation rate of the whole community decreased under OA when nitrogen or phosphorus was added alone, whereas no effect was observed in other treatments. Overall our results suggested that nutrient availability may amplify or neutralize or even reverse the OA effects on marine picocyanobacteria in the South China Sea.


Key words：ocean acidification, nutrient availability, Synechococcus, Prochlorococcus, the South China Sea