Variations de la concentration bactérienne dans les eaux et les sédiments littoraux

Bacterial counts, carried out bi-mouthly over 2 years, at diverse localities on the Provence shores (France), revealed that the bottom-water microflora is not dependent on chemical and biological characteristics of the upper sediment layer. Freshwater inflow, polluted or non-polluted, and high concentrations of suspended particulate matter usually induce the highest bacterial counts. The concentration of microflora in marine muds and sands is connected with their organic content. There is no apparent correlation with water microflora concentration or macrobenthos density. The area of highest bacterial concentration is restricted to a narrow, thin belt of littoral sediment. Bacterial transformation is probably more important in the water mass as a whole than in marine deposits. The annual range of variations in microflora distribution is higher than the range which was encountered when testing the validity of the bacterial count method with the sampling technique employed. Certain bacterial concentrations, appearing simultaneously in different sediment layers and at different stations seem to be related to ecological factors. Such variations seem to realize a true annual cycle. The highest counts occur during the warm season, unlike the phytoplankter populations. Bacterial proliferation in water masses usually succeeds to phytoplankton blooms.