A future, more acidic ocean could be less productive, despite the fertilizing effects of elevated CO2. Reconciling pH and future productivity The differential effects of reduced seawater pH and increased carbon dioxide on marine phytoplankton productivity have not been resolved. Hong et al. found that previous experimentation did not account for variable metal concentrations or for ammonia contamination. After controlling for these variables, experimentation, protein expression analysis, and field data showed that low pH, coupled with the low ambient iron availability in the open ocean, inhibits nitrogen fixation, whereas elevated CO2 is fertilizing. Overall, the deleterious effects of decreased pH trump the beneficial effects of increased CO2. Thus, it seems that in a future, more acidic ocean, phytoplankton productivity is likely to be suppressed. Science, this issue p. 527 Acidification of seawater caused by anthropogenic carbon dioxide (CO2) is anticipated to influence the growth of dinitrogen (N2)–fixing phytoplankton, which contribute a large fraction of primary production in the tropical and subtropical ocean. We found that growth and N2-fixation of the ubiquitous cyanobacterium Trichodesmium decreased under acidified conditions, notwithstanding a beneficial effect of high CO2. Acidification resulted in low cytosolic pH and reduced N2-fixation rates despite elevated nitrogenase concentrations. Low cytosolic pH required increased proton pumping across the thylakoid membrane and elevated adenosine triphosphate production. These requirements were not satisfied under field or experimental iron-limiting conditions, which greatly amplified the negative effect of acidification.

中文翻译：

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海洋酸化对突出的固氮蓝藻 Trichodesmium 的复杂影响

尽管二氧化碳含量升高会产生肥沃的影响，但未来酸性更强的海洋的生产力可能会降低。协调 pH 值和未来生产力 海水 pH 值降低和二氧化碳增加对海洋浮游植物生产力的不同影响尚未解决。洪等人。发现之前的实验没有考虑到可变的金属浓度或氨污染。在控制了这些变量后，实验、蛋白质表达分析和现场数据表明，低 pH 值加上开阔海洋中环境铁的可用性低，会抑制固氮，而升高的二氧化碳则会施肥。总体而言，降低 pH 值的有害影响胜过增加 CO2 的有益影响。因此，似乎在未来，更酸的海洋，浮游植物的生产力可能会受到抑制。科学，这个问题 p。527 由人为二氧化碳 (CO2) 引起的海水酸化预计会影响固氮 (N2) 浮游植物的生长，浮游植物在热带和亚热带海洋中占初级生产的很大一部分。我们发现在酸化条件下，无处不在的蓝藻 Trichodesmium 的生长和 N2 固定减少，尽管高 CO2 的有益影响。尽管固氮酶浓度升高，但酸化导致低胞质 pH 值和 N2 固定率降低。低细胞质 p​​H 值需要增加跨类囊体膜的质子泵送和增加三磷酸腺苷的产生。这些要求在现场或实验铁限制条件下不满足，