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

海岸带缺氧（氧耗竭）既有自然的因素，也有越来越多的人为因素，这些因素可能导致大陆架上发生的生物地球化学过程发生变化。众所周知，大陆架区域是陆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的发展过程中，从海岸带和大陆架沉积物上覆水柱铁的流出率。在选定的研究地点在墨西哥湾，并在以前从秘鲁和纳米比亚大陆边缘取样的材料进行测试的基本假设是，发生在这些大陆架沉积物的氧化还原梯度将提供增加通量率和特征同位素轻铁签名缺氧的发展。如果缺氧的程度过渡到硫化物沉积物制度，底栖铁通量可能会减少在负反馈回路由于溶解度的限制，但甚至更轻的同位素Fe逃逸到水柱。 一个更好地了解成岩交付通量的铁，浮游植物生长所必需的微量营养素，从沉积物中寻求占全球海洋生产力的平衡在不断变化的海洋条件下。铁同位素系统学追踪沿海底栖铁来源的能力是这项研究的一个潜在的变革性成果。这项工作还将加强美国和德国研究人员之间的国际合作，并提供一个机会，以发展这些想法的方法，如用于底层水取样的底栖室，以及沉积物孔隙流体和核心孵化，以及水柱同位素研究。 还将开展一系列教育和外联活动。

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.