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Answer: Marine snow is a shower of mostly biological debris that originates in the top layers of the ocean and drifts to the seafloor. It is a primary source of energy for animals in the deep ocean.

What it is made of

Marine snow starts in surface waters, primarily composed of phytoplankton and microbes. As the material sinks, it collects other floating debris, including fecal material, dead and decaying animals, suspended sediments such as silt, and organic material that may have been transported from the land to the sea. It also includes sand, soot, and other inorganic dust.

Why "snow"

It is called marine snow because it looks a bit like the white fluffy stuff that falls on land. Some flakes fall for weeks before finally reaching the ocean floor.

A forest-floor comparison

As plants and animals near the surface die and decay, they fall toward the seafloor, just like leaves and decaying material fall onto a forest floor.

Who eats it

Many animals in the dark parts of the ocean filter marine snow from the water or scavenge it from the seabed as their primary food source. Scientists have measured the usable material in marine snow and found plenty of carbon and nitrogen to feed many of the deep-ocean scavengers.

Claims

• id: C1 claim: Marine snow is a primary energy source for deep-ocean animals. source: S1 evidence: "providing a primary source of energy for animals in the deep ocean."
• id: C2 claim: Marine snow includes fecal matter, sand, soot, and inorganic dust. source: S2 evidence: "marine snow also includes fecal matter, sand, soot, and other inorganic dust."
• id: C3 claim: Some marine snow flakes fall for weeks before reaching the floor. source: S2 evidence: "Some flakes fall for weeks before finally reaching the ocean floor."

Sources

• [S1] What is "marine snow"? - NOAA Ocean Exploration. NOAA. https://oceanexplorer.noaa.gov/facts/marinesnow.html . License: US government work, public domain. Accessed 2026-11-04.
• [S2] What is marine snow?. NOAA. https://oceanservice.noaa.gov/facts/marinesnow.html . License: US government work, public domain. Accessed 2026-11-04.

License: this note is CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Summary by iinventedlight (AI-assisted).

@misc{iil_note_5fz5r8gw,
  author = {{iinventedlight}},
  title = {{Marine snow: the food that falls to the deep sea}},
  howpublished = {iinventedlight Library},
  year = {2026},
  date = {2026-11-04},
  url = {https://iinventedlight.com/library/notes/marine-snow/},
  note = {Permanent ID iil:note:5fz5r8gw. License: CC-BY-4.0.},
}

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