The Physicochemical Speciation of Dissolved Iron in the Bering Sea, Alaska

Authors

Kristen N. Buck, University of South FloridaFollow
Kenneth W. Bruland, University of California, Santa Cruz

Document Type

Article

Publication Date

9-27-2007

Digital Object Identifier (DOI)

https://doi.org/10.4319/lo.2007.52.5.1800

Abstract

The physicochemical speciation of dissolved iron (Fe) across natural dissolved Fe gradients in the oceanic and shelf domains of the southeastern Bering Sea was examined in surface and subsurface samples using competitive ligand exchange‐adsorptive cathodic stripping voltammetry with the added ligand salicylaldoxime. Two ligand classes were measured in all samples, a stronger L₁ ligand class and a weaker L₂ ligand class. Conditional stability constants for both ligand classes were comparable between surface and subsurface samples, with mean log K^cond_FeL1,Fe⁰ = 11.5 ± 0.3 and mean log K^cond_FeL2,Fe⁰ = 10.3 ± 0.3 in surface samples, and mean log K^cond_FeL1,Fe⁰ = 11.4 ± 0.2 with a weaker ligand and mean log K^cond_FeL2,Fe⁰ of 10.2 ± 0.2 in subsurface samples. The concentrations of dissolved Fe were strongly correlated with ambient stronger L₁ ligand concentrations for all samples with dissolved Fe concentrations greater than 0.2 nmol L⁻¹. In samples with dissolved Fe concentrations less than 0.2 nmol L⁻¹, large and variable excesses of L₁ ligand concentrations were measured, coincident with observed Fe stress or limitation on the ambient phytoplankton. These observations suggest that the phytoplankton community is readily able to access dissolved Fe from the FeL₁ complex, resulting in excess L₁ in these waters. The available speciation data from other sources indicate that a significant correlation exists between dissolved Fe and L₁ ligand concentrations in samples with intermediate dissolved Fe, and this is a seemingly ubiquitous feature of dissolved Fe cycling in the marine environment.

Was this content written or created while at USF?

Yes

Citation / Publisher Attribution

Limnology and Oceanography, v. 52, issue 5, p. 1800-1808

Scholar Commons Citation

Buck, Kristen N. and Bruland, Kenneth W., "The Physicochemical Speciation of Dissolved Iron in the Bering Sea, Alaska" (2007). Marine Science Faculty Publications. 620.
https://digitalcommons.usf.edu/msc_facpub/620