Use of nitrifying activity measurements for describing the effect of salinity on nitrification in the Scheldt estuary.

Nitrifying activity measurements, carried out on freshly collected samples from an estuarine environment, show that the composition of the nitrifier population undergoes a progressive modification during the mixing of freshwater masses in seawater, with increasing tolerance to salt. As a result, the overall effect of increasing salinity on nitrification is much less severe than the direct effect of salt on the freshwater nitrifying population.