Microflores sulfatoreductrices en milieu subantarctique. Relations avec quelques parametres physicochimiques et biologiques. (Microflores totales et heterotrophes)

The archipelago of Kerguelen with its complex fjord distribution is particularly interesting for the study of anoxic systems. Between 1968 and 1972, several stations were investigated fortnightly. One of these was further sampled weekly throughout 1982. Each sample series of sediment included the superficial aerobic and subsuperficial anaerobic levels. Each level was examined for direct epifluorescent counts, heterotrophic and sulfate-reducing bacterial numbers by M.P.N. methods, organic carbon and sulfide measurements. Sulfate-reducing bacteria seemed less related to total biomass than the heterotrophic microflora, the latter being dependent on organic supplies. The hydrogen sulfide production was directly related to the presence of sulfate reducers; however, there was accumulation only if physical conditions of the sediment allowed it. Sulfate reduction played an essential role in anoxic control but had a limited influence on the mineralization of organic input.