1] Department of Earth and Ocean Sciences, University of South Carolina, Columbia, South Carolina 29208, USA [2] Institute of Geochemistry and Petrology, Eidgenössische Technische Hochschule Zürich, NW D81.4, Clausiusstrasse 25, 8092 Zürich, Switzerland.
Department of Earth and Ocean Sciences, University of South Carolina, Columbia, South Carolina 29208, USA.
Nature. 2014 Jul 10;511(7508):212-5. doi: 10.1038/nature13482. Epub 2014 Jul 2.
Dissolved iron is an essential micronutrient for marine phytoplankton, and its availability controls patterns of primary productivity and carbon cycling throughout the oceans. The relative importance of different sources of iron to the oceans is not well known, however, and flux estimates from atmospheric dust, hydrothermal vents and oceanic sediments vary by orders of magnitude. Here we present a high-resolution transect of dissolved stable iron isotope ratios (δ(56)Fe) and iron concentrations ([Fe]) along a section of the North Atlantic Ocean. The different iron sources can be identified by their unique δ(56)Fe signatures, which persist throughout the water column. This allows us to calculate the relative contribution from dust, hydrothermal venting and reductive and non-reductive sedimentary release to the dissolved phase. We find that Saharan dust aerosol is the dominant source of dissolved iron along the section, contributing 71-87 per cent of dissolved iron. Additional sources of iron are non-reductive release from oxygenated sediments on the North American margin (10-19 per cent), reductive sedimentary dissolution on the African margin (1-4 per cent) and hydrothermal venting at the Mid-Atlantic Ridge (2-6 per cent). Our data also indicate that hydrothermal vents in the North Atlantic are a source of isotopically light iron, which travels thousands of kilometres from vent sites, potentially influencing surface productivity. Changes in the relative importance of the different iron sources through time may affect interactions between the carbon cycle and climate.
溶解态铁是海洋浮游植物的必需微量营养元素，其可利用性控制着整个海洋的初级生产力和碳循环模式。然而，不同铁源对海洋的相对重要性并不为人所知，大气尘埃、热液喷口和海洋沉积物的通量估算相差几个数量级。在这里，我们呈现了沿北大西洋一段的溶解态稳定铁同位素比值（δ(56)Fe）和铁浓度（[Fe]）的高分辨率横剖面。不同的铁源可以通过其独特的δ(56)Fe 特征来识别，这些特征在水柱中持续存在。这使我们能够计算尘埃、热液喷口以及还原性和非还原性沉积物释放对溶解相的相对贡献。我们发现，撒哈拉尘埃气溶胶是该剖面中溶解铁的主要来源，占溶解铁的 71-87%。铁的其他来源包括北美的富氧沉积物的非还原性释放（10-19%）、非洲边缘的还原性沉积物溶解（1-4%）和大西洋中脊的热液喷口（2-6%）。我们的数据还表明，北大西洋的热液喷口是同位素轻铁的来源，这种铁从喷口处输送数千公里，可能会影响表层生产力。不同铁源的相对重要性随时间的变化可能会影响碳循环与气候之间的相互作用。
