Far below the sunlit surface of the ocean, a constant shower of whitish particles drifts through the darkness. This phenomenon is called marine snow, a term coined by explorer William Beebe. This descent of material connects the vibrant life at the surface with the deep sea.
The Composition of Marine Snow
Marine snow is not frozen water but a rich mixture of mostly organic detritus. Its primary components originate in the upper ocean and include the remains of dead microscopic plants (phytoplankton) and animals (zooplankton). These particles collect other floating debris as they drift downwards.
The composition also features fecal pellets from marine creatures and discarded mucus. This organic matrix is supplemented by inorganic matter, such as sand, silt, and dust. The makeup varies based on location, season, and the life forms in the surface waters.
The Journey to the Deep
The creation of marine snow begins in the sunlit photic zone. Microscopic particles of organic waste clump together, often facilitated by sticky substances known as transparent exopolymer particles (TEP). These are secreted by bacteria and phytoplankton, binding the elements into larger, heavier flakes.
Once these aggregates form and become dense enough, they begin their slow descent to the ocean floor, a journey that can take weeks. As the flakes sink, they pass through the twilight and midnight zones of the ocean. A significant portion of the marine snow is consumed by organisms in the mid-water, never reaching the seabed.
Ecological Significance
Marine snow is a primary source of energy for deep-sea ecosystems. In the aphotic zone, where sunlight cannot penetrate for photosynthesis, organisms depend on the organic matter drifting from above. Marine snow delivers carbon and nitrogen, nourishing life from bacteria to larger scavengers on the seafloor.
Beyond being a food source, marine snow is a component of the ocean’s “biological carbon pump.” This process transports carbon from the surface into the deep sea. When phytoplankton that have absorbed carbon dioxide die, they become part of marine snow, and the carbon sinks with them.
This mechanism sequesters carbon in the deep ocean, where it can remain for hundreds or thousands of years. By transferring carbon to the depths, the biological pump helps regulate the Earth’s climate. This process removes a significant fraction of carbon dioxide from the atmosphere.