Fig 1. Conceptual diagram of the role of nitrification on the nitrogen (N) cycle in lakes.
Optimal conditions for nitrification are represented, including low light, the presence of oxygen and high ammonium (NH4+) concentrations. By controlling the availability of N forms (mainly NH4+ and nitrate–NO3-), nitrification influences phytoplankton assimilation and community structure, as well as facilitating permanent N removal through coupled nitrification-denitrification. Ammonia oxidation (AO) can be conducted by both ammonia-oxiding archaea (AOA) and ammonia-oxidizing bacteria (AOB), whereas nitrite oxidation is conducted by nitrite-oxidizing bacteria (NOB). AO also produces nitrous oxide (N2O) as a by-product, a potent greenhouse gas.