Like trees shedding leaves in a forest, the oceans are also filled with millions of particles of decaying matter that float down to the sea floor. The particles are created by the decay of plants and animals near the surface, and although they’re nicknamed “marine snow”, they’re actually composed of sand, soot, fecal matter and other inorganic dust. Over 740 million tonnes of “snow” falls to the sea floor each year, and sometimes the flakes can fall for weeks, accumulating and growing as they go. They contain plenty of carbon and nitrogen and so they provide a continuous source of food for many deep-sea creatures, who both filter it from the water and scavenge it from the sea floor. The snow that isn’t consumed joins an existing blanket of muddy ooze on the seabed, up to 10 kilometres thick, and it eventually decomposes just like fallen leaves.
These “particles of decaying matter” are known as detritus. Also, through a process called upwelling, this nutrient-rich cold, deep water is brought to the nutrient-depleted, warmer surface waters, driven by coastal and wind currents. I fucking love the ocean.