How 'Marine Snow' Impacts Ocean's Carbon Sequestration

MIT researchers find bacteria can dissolve calcium carbonate in sinking particles, slowing carbon storage.

Published on Mar. 10, 2026

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Researchers at MIT and their collaborators have found that bacteria can hitch a ride on marine snow particles and eat away at the calcium carbonate that helps the particles sink, potentially slowing the ocean's ability to sequester carbon from the atmosphere. The findings could change scientists' understanding of how quickly the ocean can store carbon and the role of microbes in the process.

Why it matters

Marine snow is a key process by which the ocean stores carbon, as phytoplankton at the surface absorb CO2 and their remains sink to the deep ocean. However, this new research suggests bacteria may be working against the ocean's carbon sequestration abilities by dissolving the calcium carbonate that helps the marine snow particles sink quickly. This could impact climate change mitigation strategies that rely on enhancing the ocean's biological pump.

The details

The researchers set up experiments to simulate sinking marine snow particles and the interactions with bacteria. They found that whenever bacteria were present, the particles rapidly lost some of their calcium carbonate ballast, which dissolved into the surrounding seawater. The amount of calcium carbonate dissolved depended on the sinking speed, with an 'intermediate' speed being the sweet spot where bacteria could most efficiently dissolve the mineral. This suggests bacteria may be a major factor in dissolving calcium carbonate in the upper ocean, even when macroscale conditions should keep it intact.

  • The study's findings were published in the Proceedings of the National Academy of Sciences in March 2026.

The players

Benedict Borer

The primary author of the study, who was a former MIT postdoc and is now an assistant professor of marine and coastal sciences at the Rutgers School of Environmental and Biological Sciences.

Andrew Babbin

An associate professor in the Department of Earth, Atmospheric and Planetary Sciences at MIT and a mission director at the Climate Project at MIT, who was a co-author on the study.

Woods Hole Oceanographic Institution

The research institution where co-authors Adam Subhas and Matthew Hayden are based.

MIT's Center for Sustainability Science and Strategy

The center where co-author Ryan Woosley is a principal research scientist.

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What they’re saying

“What we've shown is that carbon may not sink as deep or as fast as one may expect. As humanity tries to design our way out of the problem of having so much CO2 in the atmosphere, we have to take into account these natural microbial mechanisms and feedbacks.”

— Andrew Babbin, Associate Professor, MIT Department of Earth, Atmospheric and Planetary Sciences (Mirage News)

“Insights from this work are vital to predict how ecosystems will respond to marine carbon dioxide removal attempts, and overall how the oceans will change in response to future climate scenarios.”

— Benedict Borer (Mirage News)

What’s next

The researchers plan to further investigate how different environmental factors, such as temperature and pH, may impact the ability of bacteria to dissolve calcium carbonate in marine snow particles.

The takeaway

This study highlights the important, yet often overlooked, role that microscale microbial processes can play in the ocean's carbon cycle and the potential limitations of relying solely on the ocean's 'biological pump' to sequester atmospheric carbon dioxide.