Collaborative Research (OSU, USC, RU): Continental Shelf Diagenesis II: The Importance of Increasing Oceanic Hypoxia to Coastal Iron Supply and the Ocean's Iron Isotope Composition

摘要：沿海地区缺氧（缺氧）既有自然因素，也有越来越多的人为因素，可能导致大陆架上发生的生物地球化学过程发生一系列变化。众所周知，大陆架区域是陆地来源和深海之间的重要过渡区。这项合作研究的目的是确定在季节性缺氧循环发展过程中铁从沿海地区和大陆架沉积物到上覆水体的流出率。在墨西哥湾选定的研究地点以及之前从秘鲁和纳米比亚大陆边缘采样的材料中进行测试的基本假设是，随着缺氧的发展，这些陆架沉积物中发生的氧化还原梯度将带来增加的通量率和特征性的较轻的同位素特征。如果缺氧程度转变为硫化物沉积状态，由于溶解度限制，底栖铁通量可能会在负反馈循环中减少，但更轻的同位素铁会逃逸到水柱中。 寻求更好地了解沉积物中成岩作用提供的铁通量（浮游植物生长的必需微量营养素），以解释海洋条件变化下海洋生产力的全球平衡。铁同位素系统学追踪沿海海底铁源的能力是这项研究的潜在变革性成果。这项工作还将加强美国和德国研究人员之间的国际合作，并提供利用底水采样的底栖室、沉积物孔隙流体和岩心孵化以及水柱同位素研究等方法来发展这些想法的机会。 还将开展一系列教育和外展活动。

AbstractCoastal zone hypoxia (oxygen depletion) has both natural and, increasingly, anthropogenic dimensions that can lead to host of changes to the biogeochemical processes taking place on continental shelves. Continental shelf regions are well known to be important transition zones between terrestrial sources and the deep ocean. The objectives of this collaborative study are to determine the efflux rates of iron from coastal zone and continental shelf sediments to overlying water columns during the development of seasonal anoxia cycles. The underlying hypothesis being tested at selected study sites in the Gulf of Mexico, and on previously sampled materials from Peru and Namibia continental margins, is that the redox gradients occurring in these shelf sediments will deliver both increasing flux rates and with characteristically isotopically lighter Fe signatures as anoxia develops. If the extent of anoxia transitions to a sulfidic sediment regime, the benthic iron flux may decrease in a negative feedback loop due to solubility constraints, but with even lighter isotopic Fe escaping to the water column. A better understanding of the diagenetically delivered flux of iron, an essential micronutrient for phytoplankton growth, from sediments is sought to account for the global balance of ocean productivity under changing oceanic conditions. The ability of Fe-isotopic systematics to trace coastal benthic iron sources is a potentially transformative outcome of this research. The work will also strengthen the international collaboration between US, and German researchers, and provide an opportunity to develop these ideas with methodologies such as benthic chambers for bottom water sampling, as well as sediment pore fluids and core incubations, and water column isotopic studies. A range of educational and outreach activities will also be carried out.