Nitrification, Denitrification and Nitrate Reduction Rates in the Sediment of Hiroshima Bay, Japan

Nitrification, denitrification and nitrate reduction rates in the sediments at two stations in Hiroshima Bay were studied seasonally from August 1994 to May 1995. The acetylene (C2H2) inhibition technique was used to evaluate the rate of these processes. The seasonal average of nitrification and denitrification rates ranged from 0.00 to 299 μg atN m–2h–1 and 0.00 to 69.0 μg atN m–2h–1, respectively. These two processes showed seasonal variations which mainly depended on the temperature of the sediment and the concentration of dissolved oxygen in the overlying water. In the present study, 11% of NO3 produced by nitrification was estimated to be denitrified as an average for a whole year. The seasonal average of NO3 reduction rate ranged from 0.00 to 794 μg atN m–2h–1. The denitrification rate accounted for only 3% of the total NO3 reduction rate.