Iron cycling in continental margin sediments and the nutrient and oxygen balance of the ocean

ICONOX研究小组评估了一个新概念，根据该概念，沉积铁循环控制着海洋的营养和氧气平衡。铁是一种必需的微量营养素，通常被认为是海洋初级生产、碳输出和呼吸耗氧量的关键限制因素。目前观测到的全球变暖导致的海洋脱氧趋势促进了海底铁矿物的溶解，由此导致的向海洋供应铁的增加可能会促进固氮、初级生产和进一步的氧气减少，形成一个正反馈循环。相反，地质记录中缺氧和硫化物环境下沉积物中铁的富集表明，在极端海洋缺氧条件下，海洋沉积物成为生物可利用铁的高效汇。从铁的释放到铁的保留和埋藏的转变可能代表了海洋中氮和碳的长期循环中一个重要的，但缺乏约束的关键。在ICONOX项目中，观测、实验和数值方法被应用于限制沉积铁的埋藏和释放在海洋生物地球化学动力学中的作用，今天和地球的历史。在项目延长12个月的框架内，计划调查化学风化对陆地和海洋的影响，以及海岸侵蚀对铁和其他元素的海洋生物地球化学循环的影响。

The ICONOX research group evaluates a novel concept according to which sedimentary iron cycling controls the ocean’s nutrient and oxygen balance. Iron is an essential micronutrient and commonly regarded as the key‐limiting factor for primary production, carbon export and respiratory oxygen consumption in the ocean. The currently observed trend of ocean deoxygenation as a consequence of global warming promotes dissolution of iron minerals at the seafloor and the resulting increase in iron supply to the ocean may fuel nitrogen fixation, primary production and further oxygen drawdown in a positive feedback loop. In contrast, notorious iron enrichments in sediments of anoxic and sulfidic settings in the geological record indicate that under conditions of extreme ocean anoxia, marine sediments turn into a highly efficient sink for bioavailable iron. The switch from iron release to iron retention and burial likely represents an important, yet poorly constrained linchpin in the long‐term cycles of nitrogen and carbon in the ocean. Within the ICONOX project, observational, experimental and numerical approaches are applied to constrain the role of sedimentary iron burial and release in ocean biogeochemical dynamics, today and through Earth’s history. Within the framework of a 12-months extension of the project, it is planned to investigate the influence of chemical weathering, both on land and in the ocean, as well as coastal erosion on the marine biogeochemical cycles of iron and other elements.