11 / BIG OCEAN QUESTION

Why does ‘snow’ fall in the deep ocean?

It is not frozen water. It is the slow fall of leftovers that keeps much of the deep ocean alive.

THE SHORT ANSWER

It is a mixture of dead plankton, fecal material, mucus, dust and other particles that clump and sink. Most is consumed or decomposed on the way down, but a fraction reaches deep water and sediments.

Three things to know

Origin
Mostly surface
Photosynthetic production supplies much of the organic material.
Role
Food + carbon
Particles feed deep communities and move carbon below the surface.
Fate
Mostly recycled
Microbes and animals consume much of the flux before it reaches the floor.
01

A slow particle storm

In submersible lights, sinking flakes resemble snow. They range from tiny fragments to aggregates centimeters across. Sticky gels help small particles combine, increasing sinking speed and creating temporary packages for microbes and grazers.

02

The biological pump

Phytoplankton take up carbon dioxide near the surface. When organic material sinks, it carries some carbon away from immediate exchange with the atmosphere. Respiration returns much of it to dissolved carbon at depth, while a smaller fraction is buried in sediment for longer periods.

03

A patchy food supply

Flux changes with blooms, seasons, currents and depth. Deep-sea animals use sinking particles directly, capture them from the water or eat organisms that do. Large events—including salp falls, wood falls and carcasses—create concentrated pulses on top of the background snow.

What people usually ask

Is marine snow frozen?

No. The name describes its appearance; the particles are organic and mineral material sinking through seawater.

Does all marine snow reach the seafloor?

No. Most is eaten, fragmented or decomposed in the water column.

WANT TO CHECK US?

Here’s where the answer came from

Open the original government science or research-institution source behind this page.

01
NOAA Ocean Service — What is marine snow?

Particle composition and role in the deep-sea food supply.