PHOTOINHIBITION OF MARINE NITRIFYING BACTERIA .2. DARK RECOVERY AFTERMONOCHROMATIC OR POLYCHROMATIC IRRADIATION

Nitrifying bacteria (NH4+ and NO2- oxidizers) are capable of recovery from photoinhibition in the dark. After short-term (2 to 4 h) irradiat ions, significant differences were found between the 2 groups. NH4+ ox idizers subjected to longer wavelengths (>400 nm; 25 W m(-2)) or polyc hromatic light (15 W m(-2)) regained activity faster (0.5 to 1 h) than if exposed to shorter wavelengths (<400 nm; 25 W m(-2)) or sunlight ( 360 to 400 W m(-2)). In contrast, NO2- oxidizers only failed to recupe rate activity after sunlight and near-UV (300 to 375 nm) treatment. Ar tificial light (5 to 25 W m(-2)) did not affect nitrite oxidation. Thu s, recovery of NH4+ and NO2- oxidizing activities exhibited both dose and wavelength dependencies. These distinct recovery responses imply t hat nitrogen turnover in aquatic ecosystems depends on a number of fac tors among which light transmission properties of different water type s (i.e. from lakes, rivers, estuaries, coastal marine and oceans) and physiological differences between nitrifying bacteria play significant roles.