The effects of iron limitation on the small chlorophyte Micromonas from the Northeast Pacific Ocean

Meyer, Meredith G., White, Vincent J., Torano, Olivia, Hannoush, Heidi, Lankford, Margarita and Marchetti, Adrian (2025) The effects of iron limitation on the small chlorophyte Micromonas from the Northeast Pacific Ocean. Journal of Phycology, 61 (5). pp. 1251-1262. ISSN 0022-3646

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Abstract

Small eukaryotic phytoplankton can account for a considerable amount of biomass and primary production in high nutrient, low chlorophyll (HNLC) regions of the ocean where iron limitation is pronounced. However, the physiological and metabolic strategies these cells invoke to cope under low iron conditions and the extent to which they are responsible for new production (i.e., the fraction of primary production supported by nutrients from outside of the euphotic zone) are unclear. Here, we examined how a representative picoeukaryote—the chlorophyte Micromonas sp., recently isolated from the iron-limited subarctic Northeast Pacific Ocean—responded to iron limitation when grown on nitrate as a nitrogen source. Iron-limited Micromonas exhibited reductions in growth rate, cell volume, and elemental quotas along with a restructuring of cellular metabolism. Gene expression and metabolic pathway analyses showed evidence of strategies to mitigate iron limitation with constitutive expression of genes related to nitrogen uptake and utilization. Additionally, cellular carbon and nitrogen quotas were 20–70 fmol C · cell−1 and 3.3–20 fmol N · cell−1, respectively, as a function of iron status. Based on the measured cellular quotas, we have estimated that representative picoeukaryotes (<2 μm), such as Micromonas, in HNLC Northeast Pacific waters can account for a significant proportion of new production, supporting the need for a reconsideration of the role small eukaryotic phytoplankton play in the global carbon cycle.

Item Type:	Article
Additional Information:	Data Availability Statement: All data presented here are publicly available at the National Center for Biotechnology Information (accession numbers within ) and the Biological and Chemical Oceanography Data Management Office (project ID: 914269). ACKNOWLEDGMENTS We thank the EXPORTS Chief Scientists, D. Steinberg and J. Graff, and the Captain and crew of the R/V Roger Revelle for their roles in the initial sample collection, R. Paerl for use of a flow cytometer, and J. Graff for NP EXPORTS flow cytometry data. We also thank R. Flynn and E. Speciale for helpful comments on the manuscript. This work was supported by NASA Grant 80NSSC17K0552 and NSF Grant OCE2219973 to AM.
Uncontrolled Keywords:	iron limitation,nitrogen,picoeukaryotes,primary production,aquatic science,plant science ,/dk/atira/pure/subjectarea/asjc/1100/1104
Faculty \ School:	Faculty of Science > School of Environmental Sciences
Related URLs:	https://www.scopus.com/pages/publication...
Depositing User:	LivePure Connector
Date Deposited:	01 Sep 2026 13:11
Last Modified:	01 Sep 2026 13:11
URI:	https://ueaeprints.uea.ac.uk/id/eprint/104398
DOI:	10.1111/jpy.70079

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