The distribution and stabilisation of dissolved Fe in deep-sea hydrothermal plumes

Bennett, Sarah A.; Achterberg, Eric P.; Connelly, Douglas P.; Statham, Peter J.; Fones, Gary R.; German, Christopher R.

doi:10.1016/j.epsl.2008.01.048

Cited by 218 publications

(211 citation statements)

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“…If the dFe/ 3 He ratio of 0.9 × 10 6 mol/mol is indicative of the amount of vent-derived dFe persisting along hydrothermal plumes, then using the estimated annual loss rate of 3 He from the ocean (51) of 750 ± 200 mol/y, we estimate that the flux of dFe leaking from global vents into the deep ocean is ∼7 × 10 8 mol/y. This value is twice the hydrothermal flux reported based on Fe-binding ligand measurements near the Mid-Atlantic Ridge (43) and is ∼3% of the estimated 2.36 × 10 10 mol/y aerosol inputs of dissolved Fe into the surface ocean (21). Although this might seem to be a relatively insignificant marine Fe source compared with dust, we know that abyssal Southern Hemisphere waters eventually upwell in the Felimited Southern Ocean (20) where upper ocean productivity plays a significant role in global carbon export (52), allowing the relatively small percentage of open ocean dFe contributed by hydrothermal vents calculated here to play a disproportionately large role in global climate by its influence in the Fe-limited Southern Ocean.…”

Section: Resultsmentioning

confidence: 58%

“…These colloids would pass through the 0.4-μm filter used to operationally define dissolved Fe in this study, and due to their small size they would sink very slowly, providing a mechanism by which inorganic dFe might be carried away from vents in the dissolved fraction. Potentially a more ubiquitous pathway, recent studies have shown that organic ligands bind 4-8% of the dissolved Fe in hydrothermal plumes (42)(43)(44). This organic chelation protects the Fe from precipitation and stabilizes it in the dissolved phase as it is advected away from the vent site.…”

Section: Resultsmentioning

confidence: 99%

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Distal transport of dissolved hydrothermal iron in the deep South Pacific Ocean

Fitzsimmons

Boyle

Jenkins

2014

Proc. Natl. Acad. Sci. U.S.A.

149

125

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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 μm) 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 3 He and dissolved Mn (dFe: 3 He of 0.9-2.7 × 10 6 ). 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 μm) and colloidal (0.02-0.4 μm) 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).iron | hydrothermal vents | helium | East Pacific Rise | trace metals

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Section: Resultsmentioning

confidence: 58%

Section: Resultsmentioning

confidence: 99%

Distal transport of dissolved hydrothermal iron in the deep South Pacific Ocean

Fitzsimmons

Boyle

Jenkins

2014

Proc. Natl. Acad. Sci. U.S.A.

149

125

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“…However, the possibility of globally significant fluxes of iron escaping these mass precipitation events and entering open-ocean cycles is now being debated 3 , and two recent studies suggest that dissolved organic ligands might influence the fate of hydrothermally vented metals 4,5 . Here we present spectromicroscopic measurements of iron and carbon in hydrothermal plume particles at the East Pacific Rise mid-ocean ridge.…”

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confidence: 99%

“…4), the presence of a biologically labile and chemically complex pool of organic C in the vicinity of hydrothermal venting at the EPR has implications for microbiological cycling and chemical speciation of important elements such as Fe. The STXM images and Fe(ii,iii) maps shown in Fig.…”

mentioning

confidence: 99%

“…More recently, measurements of DOC at the Juan de Fuca ridge have demonstrated elevated concentrations in some biologically productive areas of diffuse venting 20 . Dissolved organic ligands present in non-buoyant hydrothermal plumes at the Mid-Atlantic Ridge have been found to stabilize Fe(iii) in solution (these complexes may represent 12-22% of the dissolved Fe in the deep ocean) 4 . Furthermore, organic ligands with thiol functionality and stability constants high enough to compete with the precipitation of sulphide minerals have been proposed for hydrothermal fluids 5 .…”

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Preservation of iron(II) by carbon-rich matrices in a hydrothermal plume

et al. 2009

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. Here we present spectromicroscopic measurements of iron and carbon in hydrothermal plume particles at the East Pacific Rise mid-ocean ridge. We show that organic carbon-rich matrices, containing evenly dispersed iron(II)-rich materials, are pervasive in hydrothermal plume particles. The absence of discrete iron(II) particles suggests that the carbon and iron associate through sorption or complexation. We suggest that these carbon matrices stabilize iron(II) released from hydrothermal vents in the region, preventing its oxidation and/or precipitation as insoluble minerals. Our findings have implications for deep-sea biogeochemical cycling of iron, a widely recognized limiting nutrient in the oceans.The mixing of hot, chemically reduced hydrothermal fluids with cold, oxygenated deep-sea water drives the dominant inorganic reactions of polymetallic sulphide precipitation and Fe oxidation and precipitation in plumes 6 . As a consequence of seawater entrainment into rising plumes, the entire volume of the global ocean must, on average, come into contact with hydrothermal fluids and particles in a relatively short time, 4000-8000 yr. Much of the trace element chemical reactivity observed in plumes is attributed, but has not been firmly linked, to the precipitation and surface reactivity of Fe oxyhydroxide minerals in both buoyant and neutrally buoyant plumes 7 . The rate of hydrothermal Fe(ii) oxidation has been correlated with the redox state of local deep waters 8 ; however, roles for dissolved organic carbon 9 (DOC) and microbial activity 10 have also been hypothesized. Although hydrothermal plume processes influence important global ocean elemental cycles, there is little mechanistic information available about these processes owing to the dynamic character of the plume environment and the complexity of plume particles. Most knowledge of plume mineral composition and reactivity is inferred from either bulk digestion of filtered solids 7 or scanning electron microscopy with elemental analysis 6 . Here we use synchrotron-based X-ray absorption spectromicroscopy to investigate Fe and C speciation at the

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Particle dynamics in the rising plume at Piccard Hydrothermal Field, Mid‐Cayman Rise

Estapa

Breier

German

2015

Geochem Geophys Geosyst

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Processes active in rising hydrothermal plumes, such as precipitation, particle aggregation, and biological growth, affect particle size distributions and can exert important influences on the biogeochemical impact of submarine venting of iron to the oceans and their sediments. However, observations to date of particle size distribution within these systems are both limited and conflicting. In a novel buoyant hydrothermal plume study at the recently discovered high-temperature (3988C) Piccard Hydrothermal Field, MidCayman Rise, we report optical measurements of particle size distributions (PSDs). We describe the plume PSD in terms of a simple, power-law model commonly used in studies of upper and coastal ocean particle dynamics. Observed PSD slopes, derived from spectral beam attenuation and laser diffraction measurements, are among the highest found to date anywhere in the ocean and ranged from 2.9 to 8.5. Beam attenuation at 650 nm ranged from near zero to a rarely observed maximum of 192 m 21 at 3.5 m above the vent. We did not find large (>100 lm) particles that would settle rapidly to the sediments. Instead, beam attenuation was well-correlated to total iron, suggesting the first-order importance of particle dilution, rather than precipitation or dissolution, in the rising plume at Piccard. Our observations at Piccard caution against the assumption of rapid deposition of hydrothermal, particulate metal fluxes, and illustrate the need for more particle size and composition measurements across a broader range of sites, globally.

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The distribution and stabilisation of dissolved Fe in deep-sea hydrothermal plumes

Cited by 218 publications

References 61 publications

Distal transport of dissolved hydrothermal iron in the deep South Pacific Ocean

Distal transport of dissolved hydrothermal iron in the deep South Pacific Ocean

Preservation of iron(II) by carbon-rich matrices in a hydrothermal plume

Particle dynamics in the rising plume at Piccard Hydrothermal Field, Mid‐Cayman Rise

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