ABSTRACT
The C2H2 inhibition technique was employed to study seasonal denitrification potential rates in sediment slurries from tidal and subtidal sites in Belfast and Strangford Loughs, Northern Ireland. A comparison of denitrification rates obtained from this method with those obtained from the 15N-gas flux method generally showed good agreement. Depth profiles measured up to 1 m showed that denitrification decreased with depth, with highest values in the 0-5-cm fraction. For the Belfast Lough tidal system a multiple regression model was developed which explained 83% of the variation in denitrification potential. The independent variables were water content, sediment temperature, total oxidizable N in porewater and total organic N. The highest rate of denitrification potential, 2100 micromol N m(-2) h(-1), was found in areas where there was a high anthropogenic input of nutrients. Denitrification in sediments in both loughs can play a potentially significant role in removal of NO3- from the overlying water. In Belfast Lough the overall denitrification potential rate matched the external NO3-N inputs, whilst in Strangford Lough it exceeded it by sixfold, which suggests a potential to remove future additional anthropogenic inputs to the Lough.
