Primary vitamin B 12 limitation and widespread stress in Antarctic phytoplankton
Iron is considered the dominant limiting or colimiting nutrient for phytoplankton growth in the Southern Ocean. However, strong competition and limited biosynthesis capabilities for vitamin B 12 (cobalamin) within the microbial community creates conditions suitable for cobalamin limitation. Through a nutrient enrichment experiment in the Amundsen Sea, we show that growth in a phytoplankton community comprising diatoms and prasinophytes was limited primarily by cobalamin and secondarily by iron. Protein biomarkers across a broad area of the Southern Ocean further indicate widespread cobalamin stress within diatoms and Phaeocystis . As warming-induced melting of ice-shelves increases iron supplies in the coastal Southern Ocean, shifts from iron to cobalamin limitation favor mixotrophic flagellates with low cobalamin requirements, altering community composition and function.
Authors
- Nicole L. Schanke (ORCID: https://orcid.org/0000-0002-8990-0587)
- Cecilia Balestra (ORCID: https://orcid.org/0000-0003-4433-4793)
- Lauren E. Lees (ORCID: https://orcid.org/0000-0002-5595-3162)
- Soo Yoon Kim (ORCID: https://orcid.org/0000-0001-5649-620X)
- Giacomo R. DiTullio (ORCID: https://orcid.org/0000-0002-3088-5423)
- Mak A. Saito (ORCID: https://orcid.org/0000-0001-6040-9295)
- Andrew Ellis Allen (ORCID: https://orcid.org/0000-0001-5911-6081)
- Rebecca J. Chmiel (ORCID: https://orcid.org/0000-0003-1461-8744)
- Francesco Bolinesi (ORCID: https://orcid.org/0000-0003-0029-1146)
- Raffaella Casotti (ORCID: https://orcid.org/0000-0002-9876-4601)
- Robert H. Lampe (ORCID: https://orcid.org/0000-0002-0578-3935)
- Dawn M. Moran (ORCID: https://orcid.org/0000-0001-8006-6058)
- Deepa Rao
- Matthew R. McIlvin (ORCID: https://orcid.org/0000-0002-5301-8365)
- Olga Mangoni (ORCID: https://orcid.org/0000-0001-7789-0820)
- Hong Zheng (ORCID: https://orcid.org/0000-0003-0972-880X)
- Riss M Kell
Institutions
- J. Craig Venter Institute (US)
- University of California, Irvine (US)
- College of Charleston (US)
- Stazione Zoologica Anton Dohrn (IT)
- University of California San Diego (US)
- National Institute of Oceanography and Applied Geophysics (IT)
- Woods Hole Oceanographic Institution (US)
- University of Naples Federico II (IT)
Publication Details
- Journal
- bioRxiv (Cold Spring Harbor Laboratory)
- Published
- 2026-11-06
- DOI
- https://doi.org/10.64898/2026.11.05.764676
- Primary Topic
- Marine Plankton and Biogeochemistry
- Type
- preprint
Funders
- National Science Foundation
- Simons Foundation
- European Commission