Anthropogenic iron alters the spring phytoplankton bloom in the North Pacific transition zone
Industrial activities have increased the supply of iron to the ocean, but the magnitude of anthropogenic input and its ecological consequences are not well-constrained by observations. Across four expeditions to the North Pacific transition zone, we document a repeated supply of isotopically light iron from an atmospheric source in spring, reflecting an estimated 39 ± 9 % anthropogenic contribution to the surface ocean iron budget. Expression of iron-stress genes in metatranscriptomes, and evidence for colimitation of ecosystem productivity by iron and nitrogen, indicates that enhanced iron supply should spur spring phytoplankton blooms, accelerating the seasonal drawdown of nitrate delivered by winter mixing. This effect is consistent with regional trends in satellite ocean color, which show a shorter, more intense spring bloom period, followed by an earlier arrival of oligotrophic conditions in summer. Continued iron emissions may contribute to poleward shifts in transitional marine ecosystems, compounding the anticipated impacts from ocean warming and stratification.
Authors
- Nathan T. Lanning (ORCID: https://orcid.org/0000-0003-3534-8587)
- Angelicque White (ORCID: https://orcid.org/0000-0002-0938-7948)
- Rhea K. Foreman (ORCID: https://orcid.org/0000-0002-6607-1691)
- Tim M. Conway (ORCID: https://orcid.org/0000-0002-3069-9786)
- Nicholas J. Hawco (ORCID: https://orcid.org/0000-0002-5897-0830)
- Sacha Coesel (ORCID: https://orcid.org/0000-0001-9422-8388)
- Jessica N. Fitzsimmons (ORCID: https://orcid.org/0000-0002-9829-2464)
- Benedetto Barone (ORCID: https://orcid.org/0000-0002-1102-7837)
- James G. Allen (ORCID: https://orcid.org/0000-0002-6765-7571)
- David M. Karl (ORCID: https://orcid.org/0000-0002-6660-6721)
- Daniela König (ORCID: https://orcid.org/0000-0003-0643-1920)
- Paulina Pinedo‐González (ORCID: https://orcid.org/0000-0003-4613-1113)
- Randelle M. Bundy (ORCID: https://orcid.org/0000-0002-0600-3953)
- L. W. Juranek (ORCID: https://orcid.org/0000-0002-4922-8263)
- Emily Seelen (ORCID: https://orcid.org/0000-0003-3782-9341)
- Ryan D. Groussman (ORCID: https://orcid.org/0000-0001-7874-7217)
- Xiaopeng Bian (ORCID: https://orcid.org/0000-0002-6098-7324)
- Seth G. John (ORCID: https://orcid.org/0000-0002-8257-626X)
- Shun‐Chung Yang (ORCID: https://orcid.org/0000-0001-5355-5411)
- E. Virginia Armbrust (ORCID: https://orcid.org/0000-0001-7865-5101)
- Matthias Sieber (ORCID: https://orcid.org/0000-0001-5510-6126)
Institutions
- University of Southern California (US)
- University of Hawaiʻi at Mānoa (US)
- Statewide California Earthquake Center (US)
- Oregon State University (US)
- University of Alaska Fairbanks (US)
- University of Washington (US)
- University of South Florida (US)
- University of South Florida St. Petersburg (US)
- College of Marin (US)
- Texas A&M University (US)
Publication Details
- Journal
- Proceedings of the National Academy of Sciences
- Published
- 2025-06-02
- DOI
- https://doi.org/10.1073/pnas.2418201122
- Citations
- 5
- Primary Topic
- Marine and coastal ecosystems
- Type
- article
- Field-Weighted Citation Impact
- 8.97
Funders
- National Science Foundation
- Simons Foundation