Influence of microorganisms on the removal of nickel in tropical marine sediments (New Caledonia)

The removal of nickel in marine tropical sediments (New Caledonia) was studied in microcosms. Removal of Ni2+ was strongly enhanced by the presence of bacteria, with rates up to twofold higher than those observed under sterilized conditions. After 8 days of incubation, Ni2+ concentration in the water column ranged from 30% to 50% of the initial concentration according to sediment origin. Addition of glucose stimulated bacterial processes and resulted in a complete disappearance of Ni2+ in the water phase. Incubation under anoxic conditions slightly affects the microbial structure inferred from T-RFLP analysis irrespective of Ni2+ spiking, whereas incubation under oxic conditions resulted to moderate modification of the microbial structure, changes that might be more marked in the presence of Ni2+. Five different T-RFs were observed in almost all microcosms with relative abundance between 5% and 30%. Incubation with glucose resulted in the dominance of a common T-RF, with relative abundance up to 39%.