Document Type
Article
Publication Date
2026
DOI
10.1073/pnas.2531765123
Publication Title
Proceedings of the National Academy of Sciences 2026
Volume
123
Issue
12
Pages
e2531765123
Abstract
The marine labile dissolved organic carbon (DOC) pool is a dynamic reservoir of thousands of molecules that cycles approximately one-quarter of Earth’s primary production within days to weeks. After excretion by phytoplankton and other microbes, metabolites are rapidly consumed, resulting in low standing concentrations (picomolar to low nanomolar). Despite the decades-long search for labile DOC sources and molecular identities, marine phytoplankton exometabolomes are not well characterized, largely due to difficulties in measuring small polar molecules in saline water. Here, we profiled the exometabolomes of six axenic phytoplankton species representing key functional groups including a diatom (Thalassiosira pseudonana CCMP1335), a picoeukaryote (Micromonas commoda RCC299), a coccolithophore (Gephyrocapsa huxleyi CCMP371), a diazotrophic cyanobacterium (Crocosphaera watsonii WH8501), and two picocyanobacteria (Prochlorococcus marinus MIT9301 and Synechococcus WH8102). From these cultures, we quantified 56 amine- and alcohol-containing exometabolites representing 11 compound classes which in sum comprised up to 23.4% of phytoplankton-excreted DOC. We estimated that these phytoplankton-derived exometabolites could supply up to 5% of the daily carbon quota of the dominant heterotrophic bacterium SAR11 in the surface ocean. Substantial variations in exometabolite identity and concentration across phytoplankton taxa underscore taxonomic diversity as a key driver in the supply and composition of labile DOC. This taxonomic variation predicts geographic and seasonal differences in the distribution of marine dissolved metabolites that underpin the cycling of labile DOC back to carbon dioxide (CO2). Overall, our work suggests that phytoplankton exometabolites are key chemical currencies that mediate significant carbon fluxes within the ocean’s carbon cycle.
Rights
Copyright © 2026 the Authors
This open access article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License (CC BY-NC-ND 4.0).
Data Availability
Article states: "Raw mass spectrometry files havebeen deposited to the MetaboLights repository (https://www.ebi.ac.uk/metab-olights/) (73) and are accessible through https://www.ebi.ac.uk/metabolights/MTBLS12895 (74). Metadata exported from Skyline and MATLAB scripts used formetabolite data processing were uploaded to Zenodo (https://doi.org/10.5281/zenodo.18854382) (75). Metabolite concentration, DOC, and cell counts datahave been deposited to the designated BCO-DMO project page (https://www.bco- dmo.org/project/984095) (76–78)."
Original Publication Citation
Zhu, Y., Anderson, H. S., Salcedo, E., Miller, S. E., Longnecker, K., Soule, M. C. K., Haley, S. T., Swarr, G. J., Braakman, R., Dyhrman, S. T., & Kujawinski, E. B. (2026). Characterization of phytoplankton-excreted metabolites mediating carbon flux through the surface ocean. Proceedings of the National Academy of Sciences, 123(12), Article e2531765123. https://doi.org/10.1073/pnas.2531765123
ORCID
0000-0002-6974-4943 (Zhu)
Repository Citation
Zhu, Yuting; Anderson, Hanna S.; Salcedo, Eli; Miller, Samuel E.; Longnecker, Krista; Kido Soule, Melissa C.; Haley, Sheean T.; Swarr, Gretchen J.; Braakman, Rogier; Dyhrman, Sonya T.; and Kujawinski, Elizabeth B., "Characterization of Phytoplankton-Excreted Metabolites Mediating Carbon Flux Through The Surface Ocean" (2026). Chemistry & Biochemistry Faculty Publications. 387.
https://digitalcommons.odu.edu/chemistry_fac_pubs/387
Supporting Information
Included in
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