Marine Snow

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The continuous downward rain of organic particles - dead plankton, faecal pellets, mucus aggregates, phytodetritus - that carries surface-produced carbon into the deep ocean. It is the food supply for almost everything below the photic zone and the mechanical core of the biological carbon pump. Most of it is consumed or remineralised on the way down: published estimates put the fraction of surface primary production reaching the abyssal seafloor at only a few percent, and recent work indicates sinking particles can lose roughly half their carbon and around 60 percent of their nitrogen during descent, feeding free-living microbes en route. A process, not a place.