Marine snow
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2008-07-13T22:37:14Z
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{{ocean fisheries topics}}
[[Image:RLampitt Pelagra recovery.jpg|thumb|left|200px|[[Underway]] recovery of a [[sediment trap]] used to collect marine snow and estimate [[export production]]]]
In the deep ocean, '''marine snow''' is a continuous shower of mostly organic [[detritus]] falling from the upper layers of the water column. Its origin lies in activities within the productive [[photic zone]]. Consequently, the prevalence of marine snow changes with seasonal fluctuations in [[photosynthesis|photosynthetic]] activity and ocean currents. Thus marine snow is heavier in spring, and the reproductive cycles of some deep-sea animals are synchronized to take advantage of this{{Fact|date=March 2007}}.
Marine snow has a composition which includes: dead or dying animals and plants ([[plankton]]), [[protist]]s ([[diatom]]s), fecal matter, sand, soot and other inorganic dust. The "snowflakes" (which are more like clumps or strings) are aggregates of smaller particles held together by a sugary mucus, transparent [[exopolymer]] particles (TEPs); natural [[polymer]]s exuded as waste products by [[bacterium|bacteria]] and [[phytoplankton]]. These aggregates grow over time and may reach several centimetres in diameter, travelling for weeks before reaching the ocean floor.
However, most organic components of marine snow are consumed by [[microbe]]s, [[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]] [[ecosystem]]s: 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.
==Study==
Marine snow has begun to garner interest from [[microbiology|microbiologists]], owing to the microbial communities associated with it. Recent research indicates transported bacteria may exchange [[gene]]s with what were previously thought to be isolated populations of bacteria inhabiting the breadth of the ocean floor. 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]].
'''Export production''' is the amount of [[organic matter]] produced in the [[ocean]] by [[primary production]] that is not recycled ([[remineralisation|remineralised]]) before it sinks into the [[aphotic zone]]. Because of the role of export production in the ocean's [[biological pump]], it is typically measured in units of [[carbon]] (e.g. [[milligram|mg]] C [[square metre|m<sup>-2</sup>]] [[day|d<sup>-1</sup>]]).
The fraction of primary production that is exported to the aphotic zone is generally higher when primary production occurs in short (seasonal) bursts, than when it occurs more evenly spread out across a year.
Because of the relatively long residence time of the ocean's [[thermohaline circulation]], carbon transported into the deep ocean by the [[biological pump]] can remain out of contact with the atmosphere for more than 1000 years. Consequently, some scientists have suggested that marine snow could play a role decreasing the [[atmosphere|atmospheric]] concentration of anthropogenic [[carbon dioxide]] (and mitigate the strength of the [[greenhouse effect]]). By [[Iron fertilization|fertilising]] certain [[HNLC|unproductive regions]] of the [[world ocean]], the resulting phytoplankton blooms could, via sinking marine snow, transport extra carbon to the deep ocean.
Projected increases in ocean temperatures caused by [[global warming]] may result in a decrease in the production of marine snow via the enhanced [[stratification (water)|stratification]] of the water column. Increasing stratification decreases the availability of phytoplankton nutrients such as [[nitrate]], [[phosphate]] and [[silicic acid]], and could lead to a decrease in primary production and, thus, marine snow.
== See also ==
* [[Biological pump]]
* [[Detritivore]]
* [[f-ratio]]
* [[Sediment trap]]
== External links ==
* [http://www.spaceref.com/news/viewpr.html?pid=5897 SpaceRef.com, Deep sea bacteria get new genes from marine snow]
* [http://halodule.marsci.uga.edu/Research/marine_snow.html U. Georgia, Marine Snow and Particles]
* [http://www.sos.bangor.ac.uk/marine/mb/O3B14/Marine_snow.html U. Bangor, Marine Snow: Formation and composition]
* [http://www.niwa.cri.nz/pubs/wa/09-4/potential NIWA, What grows up must fall down: the potential impact of climate change on plankton and carbon export]
* [http://lepo.it.da.ut.ee/~olli/eutr/html/htmlBook_63.html Primary production and vertical export]
[[Category:Aquatic ecology]]
[[Category:Bioindicators]] <!-- a bioindicator of what exactly? -->
[[Category:Biological oceanography]]
[[Category:Chemical oceanography]]
[[Category:Ecological processes]]
[[Category:Fisheries science]]
[[Category:Geochemistry]]
[[Category:Oceanography]]
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