Deep ocean microbes feed on nutrients from sinking marine snow, changing how scientists see the carbon cycle

New research from the University of Southern Denmark shows that deep ocean microbes get a steady supply of nutrients from marine snow as it sinks under high pressure. The pressure forces dissolved organic matter out of the particles, and microbes consume it quickly. Lab experiments found that marine snow can lose up to half its carbon and more than half its nitrogen before reaching the seafloor. This changes how scientists think about carbon storage in the ocean. If carbon leaks out before it gets buried in sediment, less of it stays locked away long term. Instead, some of that carbon stays suspended in deep water for centuries before cycling back to the surface. That has direct implications for climate models that assume the deep ocean is a stable carbon sink. The team plans to test this in the Arctic Ocean next.