• shareshare
  • link
  • cite
  • add
auto_awesome_motion View all 2 versions
Other research product . Other ORP type . 2020

Fe(II) stability in coastal seawater during experiments in Patagonia, Svalbard, and Gran Canaria

Hopwood, Mark J.; Santana-González, Carolina; Gallego-Urrea, Julian; Sanchez, Nicolas; Achterberg, Eric P.; Ardelan, Murat V.; Gledhill, Martha; +6 Authors
Open Access
Published: 16 Mar 2020
Publisher: Copernicus Publications under license by EGU

The speciation of dissolved iron (DFe) in the ocean is widely assumed to consist almost exclusively of Fe(III)-ligand complexes. Yet in most aqueous environments a poorly defined fraction of DFe also exists as Fe(II), the speciation of which is uncertain. Here we deploy flow injection analysis to measure in situ Fe(II) concentrations during a series of mesocosm/microcosm/multistressor experiments in coastal environments in addition to the decay rate of this Fe(II) when moved into the dark. During five mesocosm/microcosm/multistressor experiments in Svalbard and Patagonia, where dissolved (0.2 µm) Fe and Fe(II) were quantified simultaneously, Fe(II) constituted 24 %–65 % of DFe, suggesting that Fe(II) was a large fraction of the DFe pool. When this Fe(II) was allowed to decay in the dark, the vast majority of measured oxidation rate constants were less than calculated constants derived from ambient temperature, salinity, pH, and dissolved O2. The oxidation rates of Fe(II) spikes added to Atlantic seawater more closely matched calculated rate constants. The difference between observed and theoretical decay rates in Svalbard and Patagonia was most pronounced at Fe(II) concentrations <2 nM, suggesting that the effect may have arisen from organic Fe(II) ligands. This apparent enhancement of Fe(II) stability under post-bloom conditions and the existence of such a high fraction of DFe as Fe(II) challenge the assumption that DFe speciation in coastal seawater is dominated by ligand bound-Fe(III) species.

91 references, page 1 of 10

Barbeau, K.: Photochemistry of organic iron(III) complexing ligands in oceanic systems, Photochem. Photobiol., 82, 1505-1516,, 2006.

Boukhalfa, H. and Crumbliss, A. L.: Chemical aspects of siderophore mediated iron transport, Biometals, 15, 325-339,, 2002.

Bowie, A. R., Achterberg, E. P., Sedwick, P. N., Ussher, S., and Worsfold, P. J.: Real-time monitoring of picomolar concentrations of iron(II) in marine waters using automated flow injectionchemiluminescence instrumentation, Environ. Sci. Technol., 36, 4600-4607,, 2002. [OpenAIRE]

Boyd, P. W., Strzepek, R., Fu, F., and Hutchins, D. A.: Environmental control of open-ocean phytoplankton groups: Now and in the future, Limnol. Oceanogr., 55, 1353-1376,, 2010.

Breitbarth, E., Gelting, J., Walve, J., Hoffmann, L. J., Turner, D. R., Hassellöv, M., and Ingri, J.: Dissolved iron (II) in the Baltic Sea surface water and implications for cyanobacterial bloom development, Biogeosciences, 6, 2397-2420,, 2009. [OpenAIRE]

Chever, F., Rouxel, O. J., Croot, P. L., Ponzevera, E., Wuttig, K., and Auro, M.: Total dissolvable and dissolved iron isotopes in the water column of the Peru upwelling regime, Geochim. Cosmochim. Ac., 162, 66-82,, 2015. [OpenAIRE]

Clayton, T. D. and Byrne, R. H.: Spectrophotometric seawater pH measurements: total hydrogen ion concentration scale calibration of m-cresol purple and at-sea results, Deep-Sea Res. Pt. I, 40, 2115-2129,, 1993.

Conway, T. M. and John, S. G.: Quantification of dissolved iron sources to the North Atlantic Ocean, Nature, 511, 212-215,, 2014.

Croot, P. and Heller, M.: The Importance of Kinetics and Redox in the Biogeochemical Cycling of Iron in the Surface Ocean, Front. Microbiol., 3, 219,, 2012. [OpenAIRE]

Croot, P. L. and Hunter, K. A.: Labile forms of iron in coastal seawater: Otago Harbour, New Zealand, Mar. Freshwater Res., 51, 193-203,, 2000.

Funded by
Ocean Food-web Patrol – Climate Effects: Reducing Targeted Uncertainties with an Interactive Network
  • Funder: European Commission (EC)
  • Project Code: 603773
  • Funding stream: FP7 | SP1 | ENV
Related to Research communities
European Marine Science Marine Environmental Science : Ocean Food-web Patrol - Climate Effects: Reducing Targeted Uncertainties with an Interactive Network