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Authigenic mineral phases as a driver of the upper-ocean iron cycle

Abstract

Iron is important in regulating the ocean carbon cycle1. Although several dissolved and particulate species participate in oceanic iron cycling, current understanding emphasizes the importance of complexation by organic ligands in stabilizing oceanic dissolved iron concentrations2,3,4,5,6. However, it is difficult to reconcile this view of ligands as a primary control on dissolved iron cycling with the observed size partitioning of dissolved iron species, inefficient dissolved iron regeneration at depth or the potential importance of authigenic iron phases in particulate iron observational datasets7,8,9,10,11,12. Here we present a new dissolved iron, ligand and particulate iron seasonal dataset from the Bermuda Atlantic Time-series Study (BATS) region. We find that upper-ocean dissolved iron dynamics were decoupled from those of ligands, which necessitates a process by which dissolved iron escapes ligand stabilization to generate a reservoir of authigenic iron particles that settle to depth. When this ‘colloidal shunt’ mechanism was implemented in a global-scale biogeochemical model, it reproduced both seasonal iron-cycle dynamics observations and independent global datasets when previous models failed13,14,15. Overall, we argue that the turnover of authigenic particulate iron phases must be considered alongside biological activity and ligands in controlling ocean-dissolved iron distributions and the coupling between dissolved and particulate iron pools.

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Fig. 1: Seasonal evolution of DFe.
Fig. 2: Observations and modelling of DFe and ligand dynamics.
Fig. 3: Seasonal evolution of PFe phases.
Fig. 4: An integrated view of the ocean iron cycle.

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Data availability

Oceanographic data collected and analysed in this study are available at https://www.bco-dmo.org/project/822807 and https://www.bco-dmo.org/dataset/888772.

Code availability

Model code is available at https://github.com/atagliab/PISCES-BAIT and output at https://doi.org/10.5281/zenodo.7378193.

References

  1. Tagliabue, A. et al. The integral role of iron in ocean biogeochemistry. Nature 543, 51–59 (2017).

    Article  ADS  CAS  PubMed  Google Scholar 

  2. Gledhill, M. & Buck, K. N. The organic complexation of iron in the marine environment: a review. Front. Microbiol. 3, 69 (2012).

    Article  PubMed  PubMed Central  Google Scholar 

  3. Johnson, K. S., Gordon, R. M. & Coale, K. H. What controls dissolved iron concentrations in the world ocean? Mar. Chem. 57, 137–161 (1997).

    Article  CAS  Google Scholar 

  4. Lauderdale, J. M., Braakman, R., Forget, G., Dutkiewicz, S. & Follows, M. J. Microbial feedbacks optimize ocean iron availability. Proc. Natl Acad. Sci. 117, 4842–4849 (2020).

    Article  ADS  CAS  PubMed  PubMed Central  Google Scholar 

  5. Parekh, P., Follows, M. J. & Boyle, E. A. Decoupling of iron and phosphate in the global ocean. Glob. Biogeochem. Cycles 19, GB2020 (2005).

    Article  ADS  Google Scholar 

  6. Whitby, H. et al. A call for refining the role of humic-like substances in the oceanic iron cycle. Sci. Rep. 10, 6144 (2020).

    Article  ADS  CAS  PubMed  PubMed Central  Google Scholar 

  7. Boyd, P. W., Ellwood, M. J., Tagliabue, A. & Twining, B. S. Biotic and abiotic retention, recycling and remineralization of metals in the ocean. Nat. Geosci. 10, 167–173 (2017).

    Article  ADS  CAS  Google Scholar 

  8. Frew, R. D. et al. Particulate iron dynamics during FeCycle in subantarctic waters southeast of New Zealand. Glob. Biogeochem. Cycles 20, GB1S93 (2006).

    Article  Google Scholar 

  9. Ohnemus, D. C., Torrie, R. & Twining, B. S. Exposing the distributions and elemental associations of scavenged particulate phases in the ocean using basin‐scale multi‐element data sets. Glob. Biogeochem. Cycles 33, 725–748 (2019).

    Article  ADS  CAS  Google Scholar 

  10. Tagliabue, A. et al. The interplay between regeneration and scavenging fluxes drives ocean iron cycling. Nat. Commun. 10, 4960 (2019).

    Article  ADS  PubMed  PubMed Central  Google Scholar 

  11. Cullen, J. T., Bergquist, B. A. & Moffett, J. W. Thermodynamic characterization of the partitioning of iron between soluble and colloidal species in the Atlantic Ocean. Mar. Chem. 98, 295–303 (2006).

    Article  CAS  Google Scholar 

  12. Fitzsimmons, J. N., Bundy, R. M., Al-Subiai, S. N., Barbeau, K. A. & Boyle, E. A. The composition of dissolved iron in the dusty surface ocean: an exploration using size-fractionated iron-binding ligands. Mar. Chem. 173, 125–135 (2015).

    Article  CAS  Google Scholar 

  13. Tagliabue, A. et al. How well do global ocean biogeochemistry models simulate dissolved iron distributions? Glob. Biogeochem. Cycles 30, 149–174 (2016).

    Article  ADS  CAS  Google Scholar 

  14. Somes, C. J. et al. Constraining global marine iron sources and ligand‐mediated scavenging fluxes with GEOTRACES dissolved iron measurements in an ocean biogeochemical model. Glob. Biogeochem. Cycles 35, e2021GB006948 (2021).

    Article  ADS  CAS  Google Scholar 

  15. Sedwick, P. N. et al. Dissolved iron in the Bermuda region of the subtropical North Atlantic Ocean: seasonal dynamics, mesoscale variability, and physicochemical speciation. Mar. Chem. 219, 103748 (2020).

    Article  CAS  Google Scholar 

  16. Martinez-Garcia, A. et al. Iron fertilization of the Subantarctic Ocean during the last ice age. Science 343, 1347–1350 (2014).

    Article  ADS  CAS  PubMed  Google Scholar 

  17. Raven, J. A., Evans, M. C. W. & Korb, R. E. The role of trace metals in photosynthetic electron transport in O2-evolving organisms. Photosynth. Res. 60, 111–150 (1999).

    Article  CAS  Google Scholar 

  18. Wade, J., Byrne, D. J., Ballentine, C. J. & Drakesmith, H. Temporal variation of planetary iron as a driver of evolution. Proc. Natl Acad. Sci. 118, e2109865118 (2021).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  19. Tagliabue, A., Aumont, O. & Bopp, L. The impact of different external sources of iron on the global carbon cycle. Geophys. Res. Lett. 41, 920–926 (2014).

    Article  ADS  CAS  Google Scholar 

  20. Buck, K. N., Sedwick, P. N., Sohst, B. & Carlson, C. A. Organic complexation of iron in the eastern tropical South Pacific: results from US GEOTRACES Eastern Pacific Zonal Transect (GEOTRACES cruise GP16). Mar. Chem. 201, 229–241 (2018).

    Article  CAS  Google Scholar 

  21. Buck, K. N., Sohst, B. & Sedwick, P. N. The organic complexation of dissolved iron along the U.S. GEOTRACES (GA03) North Atlantic Section. Deep Sea Res. II Top. Stud. Oceanogr. 116, 152–165 (2015).

    Article  ADS  CAS  Google Scholar 

  22. Gerringa, L. J. A., Rijkenberg, M. J. A., Schoemann, V., Laan, P. & de Baar, H. J. W. Organic complexation of iron in the West Atlantic Ocean. Mar. Chem. 177, 434–446 (2015).

    Article  CAS  Google Scholar 

  23. Bressac, M. et al. Resupply of mesopelagic dissolved iron controlled by particulate iron composition. Nat. Geosci. 12, 995–1000 (2019).

    Article  ADS  CAS  Google Scholar 

  24. Lamborg, C. H. et al. The flux of bio- and lithogenic material associated with sinking particles in the mesopelagic “twilight zone” of the northwest and North Central Pacific Ocean. Deep Sea Res. II Top. Stud. Oceanogr. 55, 1540–1563 (2008).

    Article  ADS  Google Scholar 

  25. Twining, B. S. et al. Differential remineralization of major and trace elements in sinking diatoms. Limnol. Oceanogr. 59, 689–704 (2014).

    Article  ADS  CAS  Google Scholar 

  26. Tagliabue, A. et al. Persistent uncertainties in ocean net primary production climate change projections at regional scales raise challenges for assessing impacts on ecosystem services. Front. Clim. 3, 738224 (2021).

    Article  Google Scholar 

  27. Gunnars, A., Blomqvist, S., Johansson, P. & Andersson, C. Formation of Fe(III) oxyhydroxide colloids in freshwater and brackish seawater, with incorporation of phosphate and calcium. Geochim. Cosmochim. Acta 66, 745–758 (2002).

    Article  ADS  CAS  Google Scholar 

  28. Feely, R. A., Trefry, J. H., Massoth, G. J. & Metz, S. A comparison of the scavenging of phosphorus and arsenic from seawater by hydrothermal iron oxyhydroxides in the Atlantic and Pacific Oceans. Deep Sea Res. A Oceanogr. Res. Pap. 38, 617–623 (1991).

    Article  ADS  CAS  Google Scholar 

  29. Homoky, W. B. et al. Iron colloids dominate sedimentary supply to the ocean interior. Proc. Natl Acad. Sci. 118, e2016078118 (2021).

    Article  CAS  PubMed  Google Scholar 

  30. Homoky, W. B. et al. Iron and manganese diagenesis in deep sea volcanogenic sediments and the origins of pore water colloids. Geochim. Cosmochim. Acta 75, 5032–5048 (2011).

    Article  ADS  CAS  Google Scholar 

  31. Fitzsimmons, J. N. & Boyle, E. A. Both soluble and colloidal iron phases control dissolved iron variability in the tropical North Atlantic Ocean. Geochim. Cosmochim. Acta 125, 539–550 (2014).

    Article  ADS  CAS  Google Scholar 

  32. Kunde, K. et al. Iron distribution in the subtropical North Atlantic: the pivotal role of colloidal iron. Glob. Biogeochem. Cycles 33, 1532–1547 (2019).

    Article  ADS  CAS  Google Scholar 

  33. Marsay, C. M., Barrett, P. M., McGillicuddy, D. J. & Sedwick, P. N. Distributions, sources, and transformations of dissolved and particulate iron on the Ross Sea continental shelf during summer. J. Geophys. Res. Oceans 122, 6371–6393 (2017).

    Article  ADS  Google Scholar 

  34. Conway, T. M. et al. Tracing and constraining anthropogenic aerosol iron fluxes to the North Atlantic Ocean using iron isotopes. Nat. Commun. 10, 2628 (2019).

    Article  ADS  PubMed  PubMed Central  Google Scholar 

  35. Tang, W. et al. Widespread phytoplankton blooms triggered by 2019–2020 Australian wildfires. Nature 597, 370–375 (2021).

    Article  ADS  CAS  PubMed  Google Scholar 

  36. Boyd, P. W., Mackie, D. S. & Hunter, K. A. Aerosol iron deposition to the surface ocean – modes of iron supply and biological responses. Mar. Chem. 120, 128–143 (2010).

    Article  CAS  Google Scholar 

  37. Bowie, A. R. et al. Biogeochemical iron budgets of the Southern Ocean south of Australia: decoupling of iron and nutrient cycles in the subantarctic zone by the summertime supply. Glob. Biogeochem. Cycles 23, GB4034 (2009).

    Article  ADS  Google Scholar 

  38. Wu, J. & Boyle, E. Iron in the Sargasso Sea: implications for the processes controlling dissolved Fe distribution in the ocean. Glob. Biogeochem. Cycles 16, 33-1–33-8 (2002).

    Article  Google Scholar 

  39. Rijkenberg, M. J. et al. The distribution of dissolved iron in the West Atlantic Ocean. PLoS One 9, e101323 (2014).

    Article  ADS  PubMed  PubMed Central  Google Scholar 

  40. Black, E. E. et al. Ironing out Fe residence time in the dynamic upper ocean. Glob. Biogeochem. Cycles 34, e2020GB006592 (2020).

    Article  ADS  CAS  Google Scholar 

  41. Wagener, T., Guieu, C. & Leblond, N. Effects of dust deposition on iron cycle in the surface Mediterranean Sea: results from a mesocosm seeding experiment. Biogeosciences 7, 3769–3781 (2010).

    Article  ADS  CAS  Google Scholar 

  42. Honeyman, B. D. & Santschi, P. H. A Brownian-pumping model for oceanic trace metal scavenging: evidence from Th isotopes. J. Mar. Res. 47, 951–992 (1989).

    Article  CAS  Google Scholar 

  43. Wu, J., Boyle, E., Sunda, W. & Wen, L. S. Soluble and colloidal iron in the oligotrophic North Atlantic and North Pacific. Science 293, 847–849 (2001).

    Article  ADS  CAS  PubMed  Google Scholar 

  44. Völker, C. & Tagliabue, A. Modeling organic iron-binding ligands in a three-dimensional biogeochemical ocean model. Mar. Chem. 173, 67–77 (2015).

    Article  Google Scholar 

  45. Misumi, K. et al. Slowly sinking particles underlie dissolved iron transport across the Pacific Ocean. Glob. Biogeochem. Cycles 35, e2020GB006823 (2021).

    Article  ADS  CAS  Google Scholar 

  46. Seferian, R. et al. Tracking improvement in simulated marine biogeochemistry between CMIP5 and CMIP6. Curr. Clim. Change Rep. 6, 95–119 (2020).

    Article  PubMed  PubMed Central  Google Scholar 

  47. Raiswell, R., Benning, L. G., Tranter, M. & Tulaczyk, S. Bioavailable iron in the Southern Ocean: the significance of the iceberg conveyor belt. Geochem. Trans. 9, 7 (2008).

    Article  PubMed  PubMed Central  Google Scholar 

  48. von der Heyden, B. P., Roychoudhury, A. N., Mtshali, T. N., Tyliszczak, T. & Myneni, S. C. Chemically and geographically distinct solid-phase iron pools in the Southern Ocean. Science 338, 1199–1201 (2012).

    Article  ADS  PubMed  Google Scholar 

  49. Curti, L. et al. Carboxyl-richness controls organic carbon preservation during coprecipitation with iron (oxyhydr)oxides in the natural environment. Commun. Earth Environ. 2, 229 (2021).

    Article  ADS  Google Scholar 

  50. Rauschenberg, S. & Twining, B. S. Evaluation of approaches to estimate biogenic particulate trace metals in the ocean. Mar. Chem. 171, 67–77 (2015).

    Article  CAS  Google Scholar 

  51. Twining, B. S. et al. Taxonomic and nutrient controls on phytoplankton iron quotas in the ocean. Limnol. Oceanogr. Lett. 6, 96–106 (2021).

    Article  CAS  Google Scholar 

  52. Rudnick, R. L. & Gao, S. in Treatise on Geochemistry, Vol. 3 (eds Holland, H. D. & Turekian, K. K.) 1–64 (Elsevier, 2003).

  53. Shelley, R. U., Morton, P. L. & Landing, W. M. Elemental ratios and enrichment factors in aerosols from the US-GEOTRACES North Atlantic transects. Deep Sea Res. II Top. Stud. Oceanogr. 116, 262–272 (2015).

    Article  ADS  CAS  Google Scholar 

  54. GEOTRACES Intermediate Data Product Group. The GEOTRACES Intermediate Data Product 2021 (IDP2021). https://doi.org/10.5285/cf2d9ba9-d51d-3b7c-e053-8486abc0f5fd (NERC EDS British Oceanographic Data Centre NOC, 2021).

  55. Kwiatkowski, L., Aumont, O., Bopp, L. & Ciais, P. The impact of variable phytoplankton stoichiometry on projections of primary production, food quality, and carbon uptake in the global ocean. Glob. Biogeochem. Cycles 32, 516–528 (2018).

    Article  ADS  CAS  Google Scholar 

  56. Ye, Y. & Völker, C. On the role of dust-deposited lithogenic particles for iron cycling in the tropical and subtropical Atlantic. Glob. Biogeochem. Cycles 31, 1543–1558 (2017).

    Article  ADS  CAS  Google Scholar 

  57. Aumont, O., Ethé, C., Tagliabue, A., Bopp, L. & Gehlen, M. PISCES-v2: an ocean biogeochemical model for carbon and ecosystem studies. Geosci. Model Dev. 8, 2465–2513 (2015).

    Article  ADS  CAS  Google Scholar 

  58. Hamilton, D. S. et al. Recent (1980 to 2015) trends and variability in daily‐to‐interannual soluble iron deposition from dust, fire, and anthropogenic sources. Geophys. Res. Lett. 47, e2020GL089688 (2020).

    Article  ADS  CAS  Google Scholar 

  59. Liu, X. & Millero, F. J. The solubility of iron in seawater. Mar. Chem. 77, 43–54 (2002).

    Article  CAS  Google Scholar 

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Acknowledgements

We thank the captains and crews of RV Atlantic Explorer and RV Endeavor and the BATS programme team for their invaluable assistance during the four project cruises. O. Antipova provided assistance in synchrotron data collection and analysis and S. Burns provided assistance with sampling at sea. The model simulations were undertaken on Barkla, part of the High Performance Computing facilities at the University of Liverpool, UK. A.T. and D.K. were supported by NERC award NE/S013547/1; P.S. and B.S. were supported by NSF award OCE-1829833; B.S.T., D.C.O. and L.E.S. were supported by NSF award OCE-1829819; K.N.B. and S.C. were supported by NSF award OCE-1829777; R.J. was supported by NSF award OCE-1829844. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science user facility operated for the DOE Office of Science by Argonne National Laboratory under contract no. DE-AC02-06CH11357.

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Authors and Affiliations

Authors

Contributions

The overarching BAIT programme was conceptualized by P.S., K.N.B., R.J., A.T., D.C.O. and B.S.T. Field and laboratory work was conducted by K.N.B., S.C., R.J., D.C.O., L.E.S., B.S., P.S., A.T. and B.S.T. This study was designed and led by A.T., alongside K.N.B., L.E.S. and B.S.T., with further contributions from O.A., P.W.B., W.B.H. and P.S. Analysis of dissolved iron, ligands and particles was performed by P.S. and B.S., K.N.B. and S.C., and L.E.S. and B.S.T., respectively. Modelling work was undertaken by A.T. Data synthesis and model-data comparisons were conducted by A.T., D.K. and L.E.S. A.T. led the drafting of the manuscript, with input from all co-authors.

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Correspondence to Alessandro Tagliabue.

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Nature thanks Kazuhiro Misumi, Brandy Toner and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Extended data figures and tables

Extended Data Fig. 1 Seasonal evolution of total and stronger ligands.

Observed and modelled total (black symbols) and stronger (red symbols) ligand concentrations (nM). Black lines are model solutions at the BATS site from the PISCES-Quota model, with varying total ligands derived from DOC (using 0.09, 0.08 and 0.07 nM LT µM DOC−1). Blue lines represent model solutions from PISCES-Quota-Fe, with either prognostic stronger ligands (solid line) or DOC-derived total weaker ligands (dashed line, using 0.09 nM LT µM DOC−1).

Extended Data Fig. 2 Seasonal evolution of excess ligands.

Observed and modelled excess total (black symbols) and strong (red symbols) ligands (both in nM). Solid and dashed black lines are model solutions at the BATS site from the PISCES-Quota model, with varying total ligands derived from DOC (using 0.09, 0.08 and 0.07 nM LT (µM DOC)−1) or prognostic stronger ligands (thin black lines). Blue lines represent model solutions from PISCES-Quota-Fe, with either prognostic stronger ligands (solid line) or DOC-derived total ligands (dashed line, using 0.09 nM LT (µM DOC)−1). Values less than zero are when DFe concentrations exceed the concentrations of either L1 or LT. Only the PISCES-Quota-Fe model is able to generate the observed large excess ligand pools.

Extended Data Fig. 3 Variations in the seasonal evolution of dissolved iron.

DFe data and model solutions at the BATS site. Red crosses are DFe data for each voyage for three stations in the BATS region. All black lines are model solutions at the BATS site from the PISCES-Quota model, with total ligands derived from DOC (using 0.09 nM LT µM DOC−1) but with varying strengths of scavenging of free Fe by lithogenic particles. Blue lines represent model solutions from the new PISCES-Quota-Fe model, with either prognostic stronger ligands (solid line) or DOC-derived total ligands (dashed line, using 0.09 nM LT (µM DOC)−1). In red, we also compare the default PISCES-Quota (solid line, with total ligands derived from DOC using 0.09 nM LT µM DOC−1) and PISCES standard (dashed line) models. This demonstrates that there is little difference in the model–data mismatch in the seasonal evolution of DFe between PISCES-Quota and the standard PISCES model.

Extended Data Fig. 4 Global model–data comparison of dissolved iron.

Observed and modelled dissolved iron (nM) for ten GEOTRACES sections for PISCES-Quota-Fe and PISCES-Quota. Observations and models are binned onto the same vertical grid.

Extended Data Fig. 5 Model performance for biogeochemical metrics.

Plots showing the difference in performance between PISCES-Quota and PISCES-Quota-Fe for a suite of biogeochemical diagnostics. Average upper 100 m NO3 and PO4 are in mmol m−3, average 200–600 m O2 is in mmol m−3, total chlorophyll (T-Chl) at the surface (summed across the picophytoplankton, nanophytoplankton and diatoms) is in mg m−3 and carbon export at 100 m is in mol m−2 year−1. It can be seen that the new PISCES-Quota-Fe model does not substantially alter the biogeochemical mean state of the model.

Extended Data Fig. 6 Iron cycle fluxes in the Atlantic and Pacific oceans.

Proportional contributions of different processes to total DFe supply and removal fluxes along two example sections in the Atlantic (20° W) and Pacific (150° W) oceans from the PISCES-Quota-Fe model with prognostic strong ligands.

Extended Data Table 1 Model–observations statistical assessment

Supplementary information

Supplementary Table 1

Previous iron-cycle-process studies. A summary of available measurements of the ocean iron cycle from time series stations and process studies that collected temporal observations. We provide the name and broad location and year of the study, the seasonal sampling frequency, depths and whether there was concurrent sampling of DFe, PFe, total ligands (Ltot), strong and weak ligands (L1 and L2) and PFe phases (lithogenic and biogenic). The current study, in the top row, is the only one to provide such data across all seasons and iron parameters.

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Tagliabue, A., Buck, K.N., Sofen, L.E. et al. Authigenic mineral phases as a driver of the upper-ocean iron cycle. Nature 620, 104–109 (2023). https://doi.org/10.1038/s41586-023-06210-5

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