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The nitrogen cycle is the biogeochemical cycle by which nitrogen is converted into multiple chemical forms as it circulates among atmospheric, terrestrial, and marine ecosystems. The conversion of nitrogen can be carried out through both biological and physical processes.
Without supplies of fixed nitrogen entering the marine cycle, the fixed nitrogen would be used up in about 2000 years. [83] Phytoplankton need nitrogen in biologically available forms for the initial synthesis of organic matter. Ammonia and urea are released into the water by excretion from plankton.
A biogeochemical cycle, or more generally a cycle of matter, [1] is the movement and transformation of chemical elements and compounds between living organisms, the atmosphere, and the Earth's crust. Major biogeochemical cycles include the carbon cycle, the nitrogen cycle and the water cycle. In each cycle, the chemical element or molecule is ...
In the marine environment, nitrogen is often the limiting nutrient, so the nitrogen cycle in the ocean is of particular interest. [36] [37] The nitrification step of the cycle is of particular interest in the ocean because it creates nitrate, the primary form of nitrogen responsible for "new" production.
Download as PDF; Printable version ... Marine cycle. Marine biogeochemical cycles ... 12 In 1898 there is a reference to the nitrogen cycle in relation to nitrogen ...
The marine nitrogen cycle consists of complex microbial transformations which include the fixation of nitrogen, its assimilation, nitrification, anammox and denitrification. [78] Some of these processes take place in deep water so that where there is an upwelling of cold waters, and also near estuaries where land-sourced nutrients are present ...
For his 1934 paper, Alfred Redfield analyzed nitrate and phosphate data for the Atlantic, Indian, Pacific oceans and Barents Sea. [1] As a Harvard physiologist, Redfield participated in several voyages on board the research vessel Atlantis, analyzing data for C, N, and P content in marine plankton, and referenced data collected by other researchers as early as 1898.