近海富营养化与海水酸化耦合背景下大型海藻固碳生理的适应机制研究

Increasing atmospheric CO2 leads to the declining pH of seawater, that is to say ocean acidification. And in coastal waters, eutrophication has been proved to aggravate such seawater acidification. Marine macroalgae, the most important primary productivity in costal waters, must be influenced by multiple variations of pH, various inorganic carbon constituents, nitrogen and phosphorus supplies, which are caused by coupling effects of eutrophication and CO2-induced acidification. In this study, two typical experiment patterns of microcosam and mesocosm will be constructed, and various conditions of acidification, nitrogen and phosphorus supplies will be set in the two patterns, respectively. The synergistic effects on carbon fixation of eutrophication and CO2-induced acidification will be investigated by means of measurements to parameters of photosynthetic carbon utilization, activity of some important enzymes, functions of inhibitors and the content of carbon metabolites in macroalgae cultured under different conditions. Meanwhile, adaptation mechanism of carbon fixation in marine macroalgae will be also revealed on the basis of analysis on light energy utilization and nitrogen metabolism. These results will help accurate evaluation and anticipation to the ecological effect of ocean acidification in future.

大气CO2浓度升高降低了海水pH值，引起了海水的酸化，而在近海，富营养化现象更加剧了海水酸化的程度。作为近海最重要的初级生产力，大型海藻面临着富营养化和海水酸化耦合效应带来的pH值、各无机碳成分、氮和磷供应等多个环境因子的协同变动，其固碳生理将受到或正或负的综合影响。 本课题将构建室内可控的微型（microcosam）和室外原位模拟的中型生态系（mesocosm）两种实验模式，选择具有不同碳利用途径的大型海藻，在两种模式下设置不同的酸化条件、不同的氮磷供应，通过对海藻适应培养后固碳特点相关参数、固碳关键酶、抑制剂影响及碳代谢产物等固碳生理过程的分析监测，探讨富营养化和海水酸化耦合效应对大型海藻固碳生理的影响，并通过对光能利用、氮代谢等相关过程的分析，揭示海藻的适应机制。本研究的预期成果将有助于对将来近海酸化生态效益进行更加准确、客观的预测与评价。

CO2引起的海洋酸化是当前备受关注的海洋环境问题，富营养化能够加剧近海海水的酸化程度。生活在近岸海水中的大型海藻将面对pH值、pCO2、氮和磷营养供应等多个环境因子的协同变动，导致大型海藻对近海富营养化和海水酸化耦合效应的生理响应变得非常复杂。本项目通过分别构建微型和中型实验生态系统，应用室内精确控制和野外原位模拟两种研究方法，探讨了大型海藻对近岸富营养化与海水酸化耦合效应固碳生理的适应机制。主要研究结果显示：CO2引起的酸化由于pH值降低同时伴随无机碳浓度增加，因而其综合效应一般能够促进大型海藻的生长和光合固碳，氮和磷供应的增加，对大型海藻的生长、光合固碳和氮利用都会起到促进作用，但对海水酸化的综合效应未见显著改变，这可能是大型海藻碳、氮物质能量代谢维系平衡所需的主动调节所致。总体来说，我们的研究结果可以为学术界准确、客观、全面的评价将来海洋酸化在近海的生态效应提供一定的理论参考。