What is marine snow and why does the deep ocean depend on it?

The answer

Marine snow is the continuous shower of organic detritus falling from the upper ocean to the deep sea. Composed of dead plankton, fecal pellets, mucus feeding webs, dust, and microorganisms, these particles range from 0.5 millimeters to several centimeters. It takes roughly two weeks for a particle to descend from the surface to 4,000 meters, during which 90 to 95 percent is consumed or decomposed by mid-water organisms. Only 1 to 3 percent of surface production reaches the abyssal floor, yet this trickle sustains the entire deep-sea food web. Marine snow also plays a critical role in the biological carbon pump, transporting an estimated 5 to 12 gigatons of carbon to the deep ocean annually - roughly equivalent to humanity's total yearly fossil fuel emissions.