Nitrogen Cycle

The above diagram depicts the major pathways, transformations, and chemical species in mat nitrogen cycling. Thickness of the arrow depicts relative abundance.
  1) Some of the atomospheric N2 that diffuses into the mat is
  2)converted to biologically utilizable NH3 via a process known as N2 fixation.
  3) Other biological utilizable nitrogen in the form of dissolved inorganic nitrogen (DIN) (NH4+ and NO3-) and dissolved organic (DON) (e.g. amino acids and nucleic acids may diffuse into the mat from the water column. Nitrogen derived from the water column and N2 fixation are considered 'new' nitrogen sources.
  4) Nitrogen incorporated into organic matter is mineralized to
  5) NH4+ through heterotrophic and degradative processes.
  6) Porewater NH4+ is the primary nitrogen source used by organisms to meet the demands of primary and bacterial production.
  7) Porewater NH4+ may be used in the autotrophic process of
  8) nitrification, which results in the production of nitrate.
  9) Nitrate may be reassimilated into biomass or

. .
  10) converted to N2 by denitrification and
  11) lost from the mat. Depending on the environment, mats may act as either or source of nitrogen for the surrounding ecosystem. In coastal areas where there are riverine inputs of nitrogen sources, mats are likely N sinks. In areas where there is no substantial terrestrial nitrogen inputs, such as reefs and Antarctic Lakes, the mats likely act as sources of nitrogen for the surrounding environment.