Phytoplankton growth in the Indian Ocean is generally limited by macronutrients (nitrogen: N and phosphorus: P) in the north and by micronutrient (iron: Fe) in the south. Increasing atmospheric deposition of N and dissolved Fe (dFe) into the ocean due to human activities can thus lead to significant responses from both the northern and southern Indian Ocean ecosystems. Previous modeling studies investigated the impacts of anthropogenic nutrient deposition on the ocean, but their results are uncertain due to incomplete representations of the Fe cycling. This study uses a state‐of‐the‐art ocean ecosystem and Fe cycling model to evaluate the transient responses of ocean productivity and carbon uptake in the Indian Ocean, focusing on the centennial time scale. The model includes three major dFe sources and represents an internal Fe cycling modulated by scavenging, desorption, and complexation with multiple, spatially varying ligand classes. Sensitivity simulations show that after a century of anthropogenic deposition, ecosystem responses in the Indian Ocean are not uniform due to a competition between the phytoplankton community. In particular, the competition between diatom, coccolithophore, and picoplankton alters the balance between the organic and carbonate pumps in the Indian Ocean, increasing the carbon uptake along 50°S and the southeastern tropics while decreasing it in the Arabian Sea. Our results reveal the important role of ecosystem dynamics in controlling the sensitivity of carbon fluxes in the Indian Ocean under the impact of anthropogenic nutrient deposition over a centennial timescale.

中文翻译：

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人为的铁沉积在百年历史上改变了印度洋的生态系统和碳平衡

在印度洋，浮游植物的生长通常受到北部北部大量营养元素（氮：N和磷：P）和南部南部微量营养元素（铁：Fe）的限制。由于人类活动，大气中N和溶解的Fe（dFe）在大气中的沉积增加，可能导致印度洋北部和南部生态系统做出重大反应。先前的建模研究调查了人为养分沉积对海洋的影响，但由于铁循环的不完整表示，其结果尚不确定。这项研究使用了最先进的海洋生态系统和铁循环模型来评估印度洋海洋生产力和碳吸收的瞬态响应，重点是百年时间尺度。该模型包括三个主要的dFe来源，代表内部的Fe循环，该循环通过清除，解吸和与多个空间变化的配体类别的络合进行调节。敏感性模拟显示，在一个世纪的人为沉积之后，由于浮游植物群落之间的竞争，印度洋的生态系统响应并不统一。特别是，硅藻，球墨石藻和微微浮游生物之间的竞争改变了印度洋有机泵和碳酸盐泵之间的平衡，增加了沿50°S和东南热带地区的碳吸收，而在阿拉伯海中则减少了。我们的结果揭示了在百年时间尺度上，在人为养分沉积的影响下，生态系统动力学在控制印度洋碳通量敏感性方面的重要作用。