above diagram depicts the major pathways, transformations, and chemical
species in mat nitrogen cycling. Thickness of the arrow depicts
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
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
8) nitrification, which results in the production
9) Nitrate may be reassimilated into biomass or