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

合作研究（俄勒冈州立大学、南加州大学、俄罗斯大学）：大陆架成岩作用 II：海洋缺氧加剧对沿海铁供应和海洋铁同位素组成的重要性

• 批准号: 1029889
• 负责人: James McManus
• 金额: $ 29.48万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-01-15 至 2014-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1029889&HistoricalAwards=false
• 关键词: Collaborative; Research; OSU; USC; RU

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.

海岸带缺氧既有自然因素的影响，也有越来越多的人为因素影响。海岸带缺氧可导致大陆架生物地球化学过程的一系列变化。众所周知，大陆架区域是陆地源与深海之间的重要过渡带。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，铁从沿海地区和大陆架沉积物到上盖水柱的外排速率。在墨西哥湾选定的研究地点以及先前从秘鲁和纳米比亚大陆边缘取样的材料上测试的基本假设是，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通量速率的增加，并且具有典型的同位素较轻的铁特征。如果缺氧程度过渡到硫化物沉积状态，由于溶解度的限制，底栖铁通量可能会以负反馈回路减少，但更轻的同位素铁会逸出到水柱中。人们试图更好地了解沉积物中铁的成岩输送通量，以解释海洋条件变化下海洋生产力的全球平衡。铁是浮游植物生长所必需的微量营养素。铁同位素系统学追踪沿海底栖铁源的能力是本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，并提供一个机会来发展这些想法，如海底取样的底栖室，以及沉积物孔隙流体和岩心孵化，以及水柱同位素研究。还将开展一系列教育和外联活动。