Nitrification or ‘ammonium oxidation’ is a two-step respiratory process occurring in sediment (benthic nitrification) or the water column (pelagic nitrification) in which bacteria oxidise ammonium (NH4) to nitrite (NO2) and nitrate (NO3).
(Eq. 1) NH4+ + 1.5O2 = NO2– + H2O + 2H+
(Eq. 2) NO3– + 0.5O2 = NO3–
Nitosomonous spp. and Nitrobacter spp. are the main organisms responsible for steps (Eq. 1) and (Eq. 2) respectively. Nitrification exerts an important influence on marine primary productivity because:
- it modifies the form of nitrogen released during the decomposition of organic matter);
- it shunts nitrogen to denitrification pathways; and
- it competes with heterotrophic bacteria for dissolved oxygen supplies . Water temperature is the most important factor regulating benthic and pelagic nitrification rates in estuaries .
- Henriksen, K, and Kemp, W.M. 1988. Nitrification in Estuarine and Coastal Marine Sediments, pp. 207-249 in T.H. Blackburn and J. Sorensen (eds.), Nitrification in Estuarine and Coastal Marine Sediments. Nitrogen Cycling in Coastal Marine Environments, John Wiley and Sons Ltd.
- Berounsky, V.M. and Nixon, S.W. 1990. Temperature and the annual cycle of nitrification in waters of Narragansett Bay. Limnology and Oceanography 35, 1610-1617.