In biological

oceanography Oceanography (), also known as oceanology, sea science, ocean science, and marine science, is the scientific study of the ocean, including its physics, chemistry, biology, and geology. It is an Earth science, which covers a wide range of to ...

, new production is supported by nutrient inputs from outside the

euphotic zone The photic zone (or euphotic zone, epipelagic zone, or sunlight zone) is the uppermost layer of a body of water that receives sunlight, allowing phytoplankton to perform photosynthesis. It undergoes a series of physical, chemical, and biological ...

, especially

upwelling Upwelling is an physical oceanography, oceanographic phenomenon that involves wind-driven motion of dense, cooler, and usually nutrient-rich water from deep water towards the ocean surface. It replaces the warmer and usually nutrient-depleted sur ...

of nutrients from deep water, but also from terrestrial and atmosphere sources (as opposite to regenerated production, which is supported by recycling of nutrients in the euphotic zone). New production depends on mixing and vertical advective processes associated with the circulation.

New and regenerated production

Bio-available nitrogen occurs in the ocean in several forms, including simple ionic forms such as nitrate (NO₃⁻), nitrite (NO₂⁻) and ammonium (NH₄⁺), and more complex organic forms such as

urea Urea, also called carbamide (because it is a diamide of carbonic acid), is an organic compound with chemical formula . This amide has two Amine, amino groups (–) joined by a carbonyl functional group (–C(=O)–). It is thus the simplest am ...

((NH2)₂CO). These forms are utilised by

autotrophic An autotroph is an organism that can convert abiotic sources of energy into energy stored in organic compounds, which can be used by other organisms. Autotrophs produce complex organic compounds (such as carbohydrates, fats, and proteins) us ...

phytoplankton Phytoplankton () are the autotrophic (self-feeding) components of the plankton community and a key part of ocean and freshwater Aquatic ecosystem, ecosystems. The name comes from the Greek language, Greek words (), meaning 'plant', and (), mea ...

to synthesise organic molecules such as

amino acids Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the Proteinogenic amino acid, 22 α-amino acids incorporated into p ...

(the building blocks of

proteins Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, re ...

). Grazing of phytoplankton by zooplankton and larger organisms transfers this organic nitrogen up the food chain and throughout the marine

food-web A food web is the natural interconnection of food chains and a graphical representation of what-eats-what in an ecological community. Position in the food web, or trophic level, is used in ecology to broadly classify organisms as autotrophs or h ...

. When nitrogenous organic molecules are ultimately metabolised by organisms, they are returned to the water column as ammonium (or more complex molecules that are then metabolised to ammonium). This is known as regeneration, since the ammonium can be used by phytoplankton, and again enter the food-web.

Primary production In ecology, primary production is the synthesis of organic compounds from atmospheric or aqueous carbon dioxide. It principally occurs through the process of photosynthesis, which uses light as its source of energy, but it also occurs through ...

fuelled by ammonium in this way is thus referred to as regenerated production. However, ammonium can also be oxidised to nitrate (via nitrite), by the process of nitrification. This is performed by different bacteria in two stages : NH₃ + O₂ → NO₂⁻ + 3H⁺ + 2e⁻ NO₂⁻ + H₂O → NO₃⁻ + 2H⁺ + 2e⁻ Crucially, this process is believed to only occur in the absence of light (or as some other function of depth). In the ocean, this leads to a vertical separation of nitrification from primary production, and confines it to the

aphotic zone The aphotic zone (aphotic from Greek prefix + "without light") is the portion of a lake or ocean where there is little or no sunlight. It is formally defined as the depths beyond which less than 1 percent of sunlight penetrates. Above the apho ...

. This leads to the situation whereby any nitrate in the water column must be from the aphotic zone, and must have originated from organic material transported there by sinking. Primary production fuelled by nitrate is, therefore, making use of a "fresh" nutrient source rather than a regenerated one. Production by nitrate is thus referred to as new production.Dugdale, R.C.; Goering, J.J. (1967). "Uptake of new and regenerated forms of nitrogen in primary productivity". Limnol. Oceanogr. 12 (2): 196–206. To sum up, production based on nitrate is using nutrient molecules newly arrived from outside the productive layer, it is termed new production. The rate of nitrate utilization remains a good measure of the new production. While if the organic matter is then eaten, respired and the nitrogen excreted as ammonia, its subsequent uptake and re-incorporation in organic matter by phytoplankton is termed recycled (or regenerated) production. The rate of ammonia utilization is, in the same sense, a measure of recycled production.Charles B. Miller; Biological Oceanography. The use of ¹⁵N-compounds makes it possible to measure the fractions of new nitrogen and regenerated nitrogen associated with the primary production in the sea.

References

{{Reflist Biological oceanography Chemical oceanography Nitrogen Oceanography

New and regenerated production

See also

References