The gooier marine snow is, the better it is at transporting carbon

In the deep sea, it never stops snowing. The type of snow that falls in the ocean, known as marine snow, is very different from the flaky geometric wonders that fall on land. Marine snow describes tiny clumps of organic and inorganic detritus—think mucus, poop, silt, dead plankton, and other microscopic remains—that continuously rain from the sunlit shallows into the profound dark of the deep ocean. This constant shower is not just a biological curiosity; it is a fundamental engine of Earth's biogeochemical cycles, helping to regulate the global climate by moving carbon from the surface waters down to the ocean floor where it can remain isolated for centuries.

Understanding how efficiently marine snow performs this task has long been a challenge for oceanographers and climate scientists. The journey from the surface to the abyssal plains is long and fraught with hazards. Much of the organic material falling through the water column is intercepted, consumed, and respired by marine organisms long before it reaches the bottom. Consequently, only a fraction of the carbon captured by phytoplankton at the surface actually makes it to the deep-sea sink. Scientists have therefore sought to understand what physical and chemical properties determine whether a particular patch of marine snow successfully completes the journey.

A new study sheds light on this crucial mechanism by focusing on the stickiness and overall consistency of the aggregates. Researchers found that the gooier the marine snow is, the better it is at transporting carbon. When the organic detritus possesses a higher degree of viscosity and cohesiveness, it behaves differently in the water column. Instead of breaking apart easily or remaining suspended as slow-falling microparticles, gooier aggregates tend to collide with other particles, sticking together to form larger, faster-sinking parcels of organic matter.

This rapid descent is the key to efficient carbon sequestration. Because the particles sink faster, they spend less time exposed to hungry microbes and detritivores in the mid-water column. More carbon successfully bypasses the biological recycling loop of the upper ocean and is safely delivered to the deep sea. The composition of the mucus and extracellular polymeric substances produced by microorganisms plays a massive role in determining this stickiness, linking microscopic biological processes to large-scale global climate regulation.

The implications of these findings extend far beyond theoretical oceanography. As global temperatures rise and ocean chemistry changes due to anthropogenic greenhouse gas emissions, the delicate biological communities responsible for producing marine snow and its constituent mucilages may also shift. Understanding the exact relationship between the viscosity of marine snow and carbon export efficiency will allow scientists to build more accurate climate models. These models are essential for predicting how the ocean's biological pump will function in a changing world, and whether it will continue to mitigate the impacts of human-induced climate change.