Denitrification potential of epilithic communities in a lotic environment

Denitrification potentials of epilithic microbial populations were assessed using the acetylene inhibition method, in which acetylene is used to block the reduction of nitrous oxide (N₂O) to nitrogen (N₂). Samples of the epilithic community were incubated in filtered river water containing modified Bushnell-Haas salts, glycerol, and yeast extract—under aerobic (0.2 atm O₂) and anaerobic (0.2 atm He) acetylene atmospheres. N₂O was produced under both atmospheres only if exogenous nitrate of nitrite was added. Denitrification potentials were typically higher when nitrite was the added electron acceptor. The rates of denitrification were temperature-and carbon-dependent and the maximum rate, 8.53 g N₂O–N per cm² per day occurred at 23°C when nitrite was the electron acceptor.