Marine snow is a shower of organic material falling from upper waters to the deep ocean.
As plants and animals near the surface of the ocean die and decay, they fall toward the sea floor, just like leaves and decaying material fall onto a forest floor. In addition to dead animals and plants, marine snow also includes fecal matter, sand, soot, and other inorganic dust.
The decaying material is referred to as “marine snow” because it looks a little bit like white fluffy bits. The “snowflakes” grow as they fall, some reaching several centimeters in diameter. Some flakes fall for weeks before finally reaching the ocean floor.
This continuous rain of marine snow provides food for many deep-sea creatures. Many animals in the dark parts of the ocean filter marine snow from the water or scavenge it from the seabed. NOAA scientists and others have measured the amount of usable material in marine snow and found that there is plenty of carbon and nitrogen to feed many of the scavengers in the deep sea.
The small percentage of material not consumed in shallower waters becomes incorporated into the muddy “ooze” blanketing the ocean floor, where it is further decomposed through biological activity. About three-quarters of the deep ocean floor is covered in this thick, smooth ooze. The ooze collects as much as six meters every million years.
Info via NOAAhttp://oceanservice.noaa.gov/facts/marinesnow.html