Factors Controlling N2 Fixation

A range of factors can affect diazotrophs, their growth and physiological performance in the oceans. These include physical factors such as temperature, light, pressure and turbulence and chemical factors such as O2, inorganic nutrient and trace metal concentrations. Light availability is of greatest importance to phototrophic diazotrophs. Oxygen is a critical factor as it can directly inhibit the nitrogenase reaction but is also necessary for respiration for energy production in heterotrophs and phototrophs that fix N2 at night. Various diazotrophs have developed strategies to avoid O2 inactivation. P and Fe are often limiting to the growth of diazotrophs and a range of mechanisms have evolved to cope with critical shortages. Many of these factors are interactive such as temperature, turbulence and O2 concentration.