期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2014
卷号：111
期号：47
页码：16654-16661
DOI：10.1073/pnas.1418778111
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceLow concentrations of the micronutrient iron in seawater are known to limit primary production and nitrogen fixation in large regions of the global ocean. Thus, it is important to constrain the sources and sinks controlling the marine dissolved iron distribution and consequent micronutrient supply to surface plankton. Although the major dissolved iron sources have been historically thought to be atmospheric dust inputs and fluxes from the continental margin, we show here the first data to our knowledge demonstrating that dissolved iron from hydrothermal vents can be transported thousands of kilometers from the venting site, which to date has only been suggested and modeled. Thus, hydrothermal vents must be considered when determining the marine dissolved iron inventory, especially in the abyssal ocean. Until recently, hydrothermal vents were not considered to be an important source to the marine dissolved Fe (dFe) inventory because hydrothermal Fe was believed to precipitate quantitatively near the vent site. Based on recent abyssal dFe enrichments near hydrothermal vents, however, the leaky vent hypothesis [Toner BM, et al. (2012) Oceanography 25(1):209-212] argues that some hydrothermal Fe persists in the dissolved phase and contributes a significant flux of dFe to the global ocean. We show here the first, to our knowledge, dFe (<0.4 {micro}m) measurements from the abyssal southeast and southwest Pacific Ocean, where dFe of 1.0-1.5 nmol/kg near 2,000 m depth (0.4-0.9 nmol/kg above typical deep-sea dFe concentrations) was determined to be hydrothermally derived based on its correlation with primordial 3He and dissolved Mn (dFe:3He of 0.9-2.7 x 106). Given the known sites of hydrothermal venting in these regions, this dFe must have been transported thousands of kilometers away from its vent site to reach our sampling stations. Additionally, changes in the size partitioning of the hydrothermal dFe between soluble (<0.02 {micro}m) and colloidal (0.02-0.4 {micro}m) phases with increasing distance from the vents indicate that dFe transformations continue to occur far from the vent source. This study confirms that although the southern East Pacific Rise only leaks 0.02-1% of total Fe vented into the abyssal Pacific, this dFe persists thousands of kilometers away from the vent source with sufficient magnitude that hydrothermal vents can have far-field effects on global dFe distributions and inventories ([≥]3% of global aerosol dFe input).
