What is Marine Snow?

Snow in the Sea

White specks of marine snow descend on sediment-covered rock in the Caribbean Sea.
White specks of marine snow descend on sediment-covered rock in the Caribbean Sea. NOAA Okeanos Explorer Program, Mid-Cayman Rise Expedition 2011, NOAA Photo Library

Did you know that it can "snow" in the ocean?  The snow in the sea isn't the same as snow on land, but it does fall from above.  

Particles in the Ocean

Ocean snow is made up of particles in the ocean, which come from several sources:

  • Like life on land, animals and plants in the ocean die, decay, eat each other, and produce wastes (yep, there's poop in the ocean). These processes produce particles.
  • There are other particles in the ocean, including bacteria, detritus, soot, and minerals.
  • The particles also include pieces of zooplankton, such as jellyfish tentacles, feeding structures (such as the mucus web cast by a sea butterfly or pteropod) and the gelatinous houses built by tunicates

Formation of Marine Snow

As these particles are produced, they sink from the ocean surface and middle of the water column to the ocean bottom in a shower of whitish particles called "marine snow."

Sticky Snowflakes

Many of the particles, such as phytoplankton, mucus and particles like jellyfish tentacles are sticky. As the individual particles are produced and descend from the top or middle of the water column, they stick together and get bigger. They may also become homes for tiny microorganisms.

As they descend, some marine snow particles get eaten and recycled all over again, while some descend all the way to the bottom and become part of the "ooze" on the ocean floor. It may take weeks for some of these "snowflakes" to reach the ocean floor. 

Marine snow is defined as particles greater than 0.5 mm in size. These particles got their name because as scientists descend through the water column in a submersible, it can look like they are moving through a snowstorm. 

Why Is Marine Snow Important?

When you break it down into its parts, which includes such things as pieces of dead bodies, plankton poop and mucus, marine snow sounds pretty gross. But it is an important food source for some marine life, especially those down at the ocean bottom in the deep sea who might not otherwise have access to nutrients higher in the water column.  

Marine Snow and the Carbon Cycle

Perhaps more importantly to us, marine snow is also a huge part of the carbon cycle. As phytoplankton do photosynthesis, they incorporate carbon into their bodies. They may also incorporate carbon into shells, or tests, made of calcium carbonate.  As phytoplankton die or get eaten, this carbon becomes part of the marine snow, either in the body parts of the plankton or in the fecal matter of animals that have ingested the phytoplankton. That marine snow settles to the ocean bottom, where the carbon dioxide is stored.  The ocean's ability to store carbon in this way reduces carbon concentrations in Earth's atmosphere and can reduce the threat of ocean acidification

mla apa chicago
Your Citation
Kennedy, Jennifer. "What is Marine Snow?" ThoughtCo, Feb. 16, 2021, thoughtco.com/marine-snow-overview-2291889. Kennedy, Jennifer. (2021, February 16). What is Marine Snow? Retrieved from https://www.thoughtco.com/marine-snow-overview-2291889 Kennedy, Jennifer. "What is Marine Snow?" ThoughtCo. https://www.thoughtco.com/marine-snow-overview-2291889 (accessed June 10, 2023).