Dynamics of Sulfate-Reducing Microorganisms (dsrAB genes) in Two Contrasting Mudflats of the Seine Estuary (France)

By combining molecular biology and biochemical approaches, the dynamics of sulfate-reducing microorganisms (SRM) was investigated in the sediments of the Seine estuary (France). Both intertidal mixing-zone and freshwater mudflats were sampled during a 1-year period; the quantification of SRM was realized by using competitive polymerase chain reaction (PCR) based on dsrAB gene amplification, previously described by Leloup et al. (2004), and sulfate reduction rate (SRR) was determined via the SO₄² radiotracer method. Throughout the year, abundance of dsrAB genes and SRR were predominantly high in the top 15 cm of the sediment. A seasonal dynamic was observed; a predominance of activity was noted during the early summer, and seems to be mainly controlled by physical–chemical parameters (temperature and dissolved organic carbon concentration) and topographic evolution of the mudflat (erosion/deposit erosion).