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. Detritus may refer to: In geology, detritus is the name for loose fragments of rock that have been worn away by erosion. ... The photic zone is the depth of the water, whether in a lake or an ocean, that is exposed to sufficient sunlight for photosynthesis to occur. ...

Marine snow has a composition which includes: dead or dying animals and plants (plankton), protists (diatoms), 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 polymers exuded as waste products by bacteria and phytoplankton. These aggregates grow over time and may reach several centimetres in diameter, travelling for weeks before reaching the ocean floor. Photomontage of plankton organisms This page is about microscopic sea creatures. ... Typical phyla Chromista Heterokontophyta Haptophyta Cryptophyta (cryptomonads) Alveolata Dinoflagellata Apicomplexa Ciliophora (ciliates) Excavata Euglenozoa Percolozoa Metamonada Rhizaria Radiolaria Foraminifera Cercozoa Archaeplastida (in part) Rhodophyta (red algae) Glaucophyta (basal archaeplastids) Amoebozoa Choanozoa Many others; classification varies Protists (IPA: ) are a diverse group of organisms, comprising those eukaryotes that are not animals... Orders Centrales Pennales Diatoms (Greek: (dia) = through + (temnein) = to cut, i. ... A polymer is a substance composed of molecules with large molecular mass consisting of repeating structural units, or monomers, connected by covalent chemical bonds. ... Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ... Diagrams of some typical phytoplankton Phytoplankton are the autotrophic component of the plankton that drift in the water column. ...

However, 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. A microorganism or microbe is an organism that is so small that it is microscopic (invisible to the naked eye). ... Photomontage of plankton organisms Plankton is the aggregate community of weakly swimming but mostly drifting small organisms that inhabit the water column of the ocean, seas, and bodies of freshwater. ... The pelagic zone is the part of the open sea or ocean comprising the water column, i. ... In marine geology and biology, benthos are the organisms and habitats of the sea floor; in freshwater biology they are the organisms and habitats of the bottoms of lakes, rivers, and creeks. ... An ecosystem, a contraction of ecological and system, refers to the collection of biotic and abiotic components and processes that comprise and govern the behavior of some defined subset of the biosphere. ...

Marine snow has begun to garner interest from microbiologists, owing to the microbial communities associated with it. Recent research indicates transported bacteria may exchange genes 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. An agar plate streaked with microorganisms Microbiology is the study of microorganisms, which are unicellular or cell-cluster microscopic organisms. ... For other meanings of this term, see gene (disambiguation). ... Biological engineering (also biosystems engineering and bioengineering) is a broad-based engineering discipline that deals with bio-molecular and molecular processes, product design, sustainability and analysis of biological systems. ... For other uses, see Pharmacy (disambiguation). ...

The prevalence of marine snow changes with seasonal fluctuations in 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. The leaf is the primary site of photosynthesis in plants. ...

The role of marine snow in the global carbon cycle may lessen the greenhouse effect to some degree: Atmospheric carbon in the form of carbon dioxide fixed by phytoplankton and subsequently transported to the ocean floor is thought to remain out of contact with the atmosphere for perhaps thousands of years. Projected elevations in ocean temperatures may result in further stratification of the water column, leading to a decreasing rate of deep-sea carbon storage. The carbon cycle is the biogeochemical cycle by which carbon is exchanged between the biosphere, geosphere, hydrosphere and atmosphere of the Earth (other astronomical objects may have similar carbon cycles, but nothing is yet known about them). ... A schematic representation of the exchanges of energy between outer space, the Earths atmosphere, and the Earth surface. ... Carbon dioxide is a chemical compound composed of one carbon and two oxygen atoms. ...

See also

• Biological pump
• F-ratio
• Sediment trap

In oceanic biogeochemistry, the biological pump is the sum of a suite of biologically-mediated processes that transport carbon from the surface euphotic zone to the oceans interior. ... In oceanic biogeochemistry, the f-ratio is the fraction of total primary production fuelled by nitrate (as opposed to that fuelled by other nitrogen compounds such as ammonium). ... Sediment traps are instruments used in oceanography to measure the quantity of sinking particulate organic (and inorganic) material in aquatic systems, usually oceans. ...

External links

• SpaceRef.com, Deep sea bacteria get new genes from marine snow
• U. Georgia, Marine Snow and Particles
• U. Bangor, Marine Snow: Formation and composition
• NIWA, What grows up must fall down: the potential impact of climate change on plankton and carbon export
• U. Southampton, Summer snow's key role in marine life