Marine snow
Because of the role of export production in the ocean's biological pump, it is typically measured in units of carbon (e.g. mg C m−2 d−1).
Mucus secreted by zooplankton (mostly salps, appendicularians, and pteropods) also contribute to the constituents of marine snow aggregates.
[4] 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.
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.
This hypothesis states that phytoplankton, microorganisms and bacteria live attached to aggregate surfaces and are involved in rapid nutrient recycling.
[5] As the aggregates slowly sink to the bottom of the ocean, the many microorganisms residing on them are constantly respiring and contribute greatly to the microbial loop.
This fraction has a much higher total mass than either phytoplankton or bacteria but is not readily available due to size characteristics of the particles in relation to potential consumers.
Aggregates that sink more quickly to the bottom of the ocean have a greater chance of exporting carbon to the deep sea floor.
[6] Once particles have aggregated to several micrometers in diameter, they begin to accumulate bacteria, since there is sufficient site space for feeding and reproduction.
For example, Kepkay et al. found that bubble coagulation leads to an increase in bacterial respiration since more food is available to them.
Seasonal variability can also have an effect on microbial communities of marine snow aggregates with concentrations being the highest during the summer.
The particulate organic carbon formed in the euphotic zone is processed by marine microorganisms (microbes), zooplankton and their consumers into organic aggregates (marine snow), which is then exported to the mesopelagic (200–1000 m depth) and bathypelagic zones by sinking and vertical migration by zooplankton and fish.
(Whitman et al., 1998) It was previously thought that due to fragmentation, bacterial communities would shift as they travel down the water column.
Studies show that microbes in the deep ocean are not dormant, but are metabolically active and must be participating in nutrient cycling by not only heterotrophs but by autotrophs as well.
[18] Dissolved inorganic carbon fixation is on similar orders of magnitude as heterotrophic microbes in the surface ocean.
Increases in ocean temperatures, a projected indicator of climate change, may result in a decrease in the production of marine snow due to the enhanced stratification of the water column.
In such an immense area there may be as yet undiscovered species tolerant of high pressures and extreme cold, perhaps finding use in bioengineering and pharmacy.
