New WHOI-led study reveals hidden “chemical currency” fueling the ocean’s carbon cycle

Woods Hole, Mass. (March 18, 2026) — A new study, led by Woods Hole Oceanographic Institution (WHOI) and Columbia University, identifies a diverse set of molecules released by marine phytoplankton that fuel microbial life and help drive Earth’s carbon cycle. While scientists know that carbon is moved through an invisible network of phytoplankton and other microbes in the surface ocean, the specific compounds have long been a mystery. These compounds are small, chemically difficult to detect in salty seawater, and are rapidly consumed by other organisms almost as soon as they are produced.

Phytoplankton, a type of microscopic organism, take in carbon dioxide and convert it into organic carbon through photosynthesis, like plants. Each year, this process moves many tens of billions of tons of carbon through the sunlit surface ocean and contributes to the oxygen in the air we breathe. These massive natural carbon flows highlight the central role the surface ocean plays in regulating Earth’s carbon cycle.

Researchers studied six phytoplankton species representing major groups of marine phytoplankton under controlled conditions. (Photo by Hanna Anderson)

“For this study, we placed six phytoplankton species representing major groups of marine phytoplankton under controlled conditions. They had the nutrients and light they needed to grow,” said Yuting Zhu, co-lead author of the study and former WHOI postdoctoral investigator, now with Old Dominion University. “Using a chemical-tagging method developed at WHOI, we were able to quantify the composition of biologically available small molecules released by globally abundant microorganisms.”

These compounds accounted for up to 23% of the dissolved organic carbon that phytoplankton released and may support a substantial share of microbial metabolism in the global ocean.

However, many bacteria are metabolic specialists, or picky eaters. The study found that different phytoplankton species release distinct combinations of metabolites, including carbon compounds also containing nitrogen, phosphorus, and sulfur. Because bacteria vary in which molecules they can consume, the chemical “menu” produced by phytoplankton helps determine which microbial communities thrive in different parts of the ocean.

“The findings help illuminate a long-standing mystery about the composition of the ‘chemical currencies’ that are moved by microbes in the surface ocean,” said Sonya Dyhrman, a co-author of the study and professor of earth and environmental sciences at Columbia University’s Lamont-Doherty Earth Observatory. “I think of it as a microbial carbon economy. By identifying the currencies produced by phytoplankton, scientists can begin to build more realistic representations of how marine microbial communities cycle billions of tons of carbon.”

To explore the broader implications, the team, also including researchers from the Massachusetts Institute of Technology and Marine Biological Laboratory, combined laboratory measurements with global ecosystem modeling. Their results suggest that phytoplankton-derived metabolites could supply up to 5 percent of the daily carbon needs of SAR11, one of the most abundant groups of bacteria in the surface ocean.

The research was conducted as part of the National Science Foundation-funded Center for Chemical Currencies of a Microbial Planet, a science and technology center that investigates how small molecules govern interactions among microorganisms across Earth’s ecosystems.

“Understanding these exchanges is critical because a huge portion of Earth’s carbon cycle passes through this microbial system, but we still don’t fully understand it,” said the center’s director and co-author of the study, WHOI Senior Scientist Elizabeth Kujawinski. “If we understand what molecules phytoplankton release and what molecules bacteria can take up, we can start building models of how these organisms interact. We think of the surface ocean as a network, where phytoplankton and bacteria are connected by molecules—some compounds feed many different bacteria, while others only support a few.”

Future studies will investigate how environmental conditions such as nutrient limitation, temperature changes, and ocean acidification alter the molecules that phytoplankton release and how microbial communities respond to those ‘chemical currencies.’

Authors: Yuting Zhu^1†△, Hanna S. Anderson^2†, Eli Salcedo³, Samuel E. Miller⁴, Krista Longnecker¹, Melissa C. Kido Soule¹, Sheean T. Haley⁵, Gretchen J. Swarr¹, Rogier Braakman⁶, Sonya T. Dyhrman^2,5, and Elizabeth B. Kujawinski^1*

Affiliations:

1. Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
2. Department of Earth and Environmental Science, Columbia University, NY, USA
3. Civil and Environmental Engineering Department, Massachusetts Institute of Technology, Cambridge, MA, USA
4. Josephine Bay Paul Center, Marine Biological Laboratory, Woods Hole, MA, USA
5. Lamont-Doherty Earth Observatory, Columbia University, New York, NY, US
6. Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA

^† These authors contributed equally to this work

^△ Current affiliation: Department of Chemistry and Biochemistry, College of Sciences, Old Dominion University, Norfolk, VA, USA

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About Woods Hole Oceanographic Institution

The Woods Hole Oceanographic Institution is a private, non-profit organization on Cape Cod, Massachusetts, dedicated to marine research, engineering, and higher education. Established in 1930, its primary mission is to understand the ocean and its interaction with the Earth as a whole, and to communicate an understanding of the ocean’s role in the changing global environment. Top scientists, engineers, and students collaborate on more than 800 concurrent projects worldwide—both above and below the waves—pushing the boundaries of knowledge and possibility.