Denitrification Associated with Periphyton Communities

Abstract

Scrapings of decomposing Cladophora sp. mats (periphyton) covering stream bed rocks produced N 2 O when incubated under N 2 plus 15% C 2 H 2 . Denitrification (N 2 O formation) was enhanced by NO 3 − and was inhibited by autoclaving, Hg 2+ , and O 2 . No N 2 O was formed in the absence of C 2 H 2 (air or N 2 atmosphere). Chloramphenicol did not block N 2 O formation, indicating that the enzymes were constitutive. In field experiments, incubation of periphyton scrapings in the light inhibited denitrification because of algal photosynthetic O 2 production. The diurnal periphyton-associated denitrification rate was estimated to be 45.8 μmol of N 2 O·m −2 ·day −1 , as determined by averaging light, aerobic plus dark, and anaerobic rates over a 24-h period.