Abstract：
Acidification of coastal waters, synergistically driven by increasing atmospheric carbon dioxide (CO2) and intensive land-derived nutrient inputs, exerts significant stresses on the biogeochemical cycles of coastal ecosystem. However, the combined effects of anthropogenic nitrogen (N) inputs and aquatic acidification on nitrification, a critical process of N cycling, remains unclear in estuarine and coastal ecosystems. Here, we showed that increased loading of ammonium (NH4+) in estuarine and coastal waters alleviated the inhibitory effect of acidification on nitrification rates but intensified the production of the potent greenhouse gas nitrous oxide (N2O), thus accelerating global climate change. Metatranscriptomes and natural N2O isotopic signatures further suggested that the enhanced emission of N2O may mainly source from hydroxylamine (NH2OH) oxidation rather than from nitrite (NO2-) reduction pathway of nitrifying microbes. This study elucidates how anthropogenic N inputs regulate the effects of coastal acidification on nitrification and associated N2O emissions, thereby enhancing our ability to predict the feedbacks of estuarine and coastal ecosystems to climate change and human perturbations.
摘要：
沿海水域酸化，通过增加大气二氧化碳（CO2）和密集的陆源养分投入协同驱动，对沿海生态系统的生物地球化学循环产生重大压力。然而,人为氮（N）输入和水生酸化对硝化作用的综合影响，N循环的关键过程，河口和沿海生态系统尚不清楚。这里,我们表明，在河口和沿海水域增加铵（NH4+）的负荷减轻了酸化对硝化速率的抑制作用，但加剧了强效温室气体一氧化二氮（N2O）的产生，从而加速全球气候变化。超转录组学和天然N2O同位素特征进一步表明，N2O的增强排放可能主要来自羟胺（NH2OH）氧化，而不是硝化微生物的亚硝酸盐（NO2-）还原途径。这项研究阐明了人为氮输入如何调节沿海酸化对硝化和相关N2O排放的影响，从而增强我们预测河口和沿海生态系统对气候变化和人类扰动的反馈的能力。
