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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.
Nitrogen enters the ocean through precipitation, runoff, or as N 2 from the atmosphere. Nitrogen cannot be utilized by phytoplankton as N 2 so it must undergo nitrogen fixation which is performed predominantly by cyanobacteria. [82] Without supplies of fixed nitrogen entering the marine cycle, the fixed nitrogen would be used up in about 2000 ...
{{Information| |Description=Diagram of the nitrogen cycle in an aquarium. |Source=Own work, drawn in Sodipodi and Inkscape by Ilmari Karonen. |Date=2005-10-2 File usage The following 4 pages use this file:
Relationship of phosphate to nitrate uptake for photosynthesis in various regions of the ocean. Note that nitrate is more often limiting than phosphate The Redfield ratio or Redfield stoichiometry is the consistent atomic ratio of carbon , nitrogen and phosphorus found in marine phytoplankton and throughout the deep oceans.
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 ...
Schematic of photosynthesis in plants. The carbohydrates produced are stored in or used by the plant. Composite image showing the global distribution of photosynthesis, including both oceanic phytoplankton and terrestrial vegetation. Dark red and blue-green indicate regions of high photosynthetic activity in the ocean and on land, respectively.
Anammox, an abbreviation for "anaerobic ammonium oxidation", is a globally important microbial process of the nitrogen cycle [1] that takes place in many natural environments. The bacteria mediating this process were identified in 1999, and were a great surprise for the scientific community. [ 2 ]
The carbon cycle of a terrestrial ecosystem. [6] Beginning with photosynthesis, water (blue) and carbon dioxide (white) from the air are taken in with solar energy (yellow), and are converted into plant energy (green). [7] 100×10 15 grams of carbon/year fixed by photosynthetic organisms, which is equivalent to 4×10 18 kJ/yr = 4×10 21 J/yr of ...