Bacteria Dissolve Marine Snow's Carbon-Trapping Ballast

New study finds microbes can slow the ocean's ability to sequester carbon by eroding particles' calcium carbonate.

Published on Mar. 10, 2026

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Researchers at MIT and collaborators have found that bacteria can dissolve the calcium carbonate in marine snow particles, which act as a key "biological pump" to draw carbon from the atmosphere into the deep ocean. The study shows that bacteria feeding on the organic matter in marine snow excrete acidic waste that dissolves the particles' ballasting calcium carbonate, slowing their descent and potentially releasing more carbon dioxide back into the atmosphere.

Why it matters

Marine snow is a critical mechanism by which the ocean sequesters carbon from the atmosphere. This new research suggests that bacteria may be working against the ocean's natural carbon-trapping abilities by dissolving the mineral ballast that helps marine snow particles sink. As humanity looks to the oceans to help mitigate climate change, understanding these microbial mechanisms will be crucial.

The details

The researchers set up experiments to simulate sinking marine snow particles and their interactions with bacteria. They found that whenever bacteria were present, the particles rapidly lost some of their calcium carbonate, which dissolved into the surrounding seawater. The amount of calcium carbonate dissolved depended on the sinking speed, with an "intermediate" speed range providing the optimal conditions for bacteria to efficiently erode the ballast.

  • 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.

Adam Subhas

A co-author on the study from the Woods Hole Oceanographic Institution.

Matthew Hayden

A co-author on the study from the Woods Hole Oceanographic Institution.

Ryan Woosley

A principal research scientist at MIT's Center for Sustainability Science and Strategy, who was a co-author on the study.

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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, Assistant Professor, Rutgers School of Environmental and Biological Sciences (Mirage News)

What’s next

The researchers plan to further investigate how different environmental factors, such as temperature and pH, may influence the rate at which bacteria dissolve calcium carbonate in marine snow particles.

The takeaway

This study highlights the important role that microscale microbial processes play in the ocean's ability to sequester carbon, which has significant implications for understanding and modeling the ocean's biological pump as a potential climate change mitigation strategy.