Marine snow particles with high viscosity transport more than six times as much carbon to the deep ocean as thinner particles, according to research published on 8 October 2026.
The continuous descent of underwater debris, known as marine snow, removes more than 10 gigatons of carbon from surface waters each year, as reported by Sciencedaily. Only about two gigatons reach depths where carbon remains stored for centuries or millennia, while bacteria break down the rest during its journey.
Researchers at UC San Diego’s Scripps Institution of Oceanography and the University of Lincoln investigated why much of the carbon fails to reach the seafloor. Their findings, published in Science, identify particle viscosity as an important factor in how quickly bacteria degrade the sinking material.
Observing the Microscopic Terrain
The project began in 2021 when Bryce Inman, then a postdoctoral researcher at Scripps Oceanography, set out to explore the problem. After four years of development, the team created a working technique in 2025 that combined 3D confocal microscopy with specialized fluorescent molecules.
Observing individual bacteria interacting with the physical structure of mucus had never been possible,
Bryce Inman, Scripps Oceanography
This imaging approach revealed intricate microscopic structures within marine snow, detailed in a companion study published on 22 July 2026 in Nature Communications. The observations showed that bacteria colonize less viscous surface regions more easily, while denser regions deeper inside resist penetration.
Bacteria can latch on to less viscous portions of each particle, but cannot reach more viscous regions until they break it down,
Bryce Inman, Scripps Oceanography
Inman compared the process to a worm inside an apple, where outer tissue is simple to enter while the core remains difficult to chew through.
Implications for Carbon Storage
Laboratory experiments confirmed that highly viscous marine snow resists bacterial fragmentation for longer periods. Computer simulations indicated these sticky particles descend to greater depths before breaking apart, allowing them to deliver more than six times as much carbon to the deep ocean compared to less viscous material, according to ScitechDaily.
The research adds funding support from the Simons Foundation and the Engineering and Physical Sciences Research Council. Beyond ocean carbon cycles, the imaging technique provides new ways to study bacterial interactions in human digestive health, kelp forests, plant root systems, and coral reefs.
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