Marine Snow

In the deep ocean, marine snow is a continuous shower of mostly organic detritus falling from the upper layers of the water column. It was first termed by the explorer William Beebe as he observed it from his bathysphere. Its origin lies in activities within the productive photic zone. Consequently, the prevalence of marine snow changes with seasonal fluctuations in photosynthetic activity and ocean currents. Marine snow is comprised of a variety of mostly organic matter, including dead or dying animals and plants (plankton), protists (diatoms), fecal matter, sand, soot and other inorganic dust.

Most trapped particles are more vulnerable to grazers than they would be as free floating individuals and can be classified as "olive green" or "gray body" cells, which are plant parts and degrading plant material. Marine snow often forms during algal blooms. As algae accumulate, they aggregate or get captured in other aggregates, both of which accelerate the sinking rate. Aggregation and sinking is actually thought to be a large component of sources for for algae loss from surface water. Most organic components of marine snow are consumed by microbes, zooplankton and other filter-feeding animals within the first 1,000 metres of their journey.

In this way marine snow may be considered the foundation of deep sea mesopelagic and
benthic ecosystems

As sunlight cannot reach them, deep-sea organisms rely heavily on marine snow as an energy source.

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.

The Oceanic Carbon Pump

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The Oceanic Carbon Pump

Just over half of all photosynthesise on Earth occurs in the seas. Carbon dioxide from the atmosphere dissolves into surface waters, where phytoplankton use it to create biomass.

Most of this phytoplankton enters the ocean food web, as other marine organisms feed on it. Some, however, aggregates with waste-products and other solids. This forms a heavier mass, which sinks to the ocean floor as 'marine snow'. Reaching the ocean floor ( mainly the Abysaal plain), a small proportion of this aggregated organic carbon gets buried in sediments and ultimately lithifies (turns into rock). However, most remains in the water, and returns to the surface during upwelling.

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Carbon drawdown

It is commonly said, that "increased phytoplankton will draw-down increased amounts of atmospheric carbon dioxide into the ocean" - but there is obviously no suction or pump.

This drawdown is due to a 'gas equilibrium' at the water-air (ocean-atmosphere) interface. Although the oceanic CO2 level is not equal to the atmospheric CO2, there is equilibrium between them. If one increases or decreases, the other will also change to reach a new equilibrium.

With an average global sea water temperature of 15 degrees Celsius, it appears that normally the CO2-concentrations by far exceed equilibrium with the ocean water. Thus, CO2 is taken up by the ocean, and there is nothing at present to suggest that the oceans are almost saturated with CO2.

Already, because of increasing levels of atmospheric CO2, changes in the oceanic-CO2 level have been detected. As oceanic CO2 increases, so does sea water acidity. The effects of this have already been seen in deformities in corals and coccoliths.

Correspondingly, as phytoplankton 'uses up' oceanic CO2, the water-air balance is again upset, as the ocean loses some of its gas content. To regain equilibrium, more is drawn-down from the atmosphere.

The gas interchange across the ocean-atmosphere interface is simply an exchange of gases in both directions. If the status quo is not equilibrium, then the total movement in one direction will be different than in the other, until equilibrium is reached.
Stormy seas and breaking waves are a particularly active area for gas interchange, as sea water and air are vigorously mixed.

Because the ocean takes in more CO2 than it gives out, it is termed a 'carbon sink'. The terresttrial carbon sinks are the forests and vegetation, which 'lock-up' carbon in their organic matter for the long term.