Mineralization pathways and thermophilic sulfate reduction in Arctic sediments, Svalbard

This study emphasizes the importance of microbial Mn(IV) and Fe(III) reduction for carbon cycling in marine arctic sediments. The relative contribution of these processes to anaerobic carbon mineralization were regulated by high concentrations of particulate Mn(IV) and Fe(III), low overall carbon mineralization rates, bioturbation and the low organic carbon content due to the extended presence of ice cover in the northern Barents Sea.Furthermore the temperature regulation of sulfate reduction (SR) was investigated in Arctic fjord sediments of Svalbard. The psychrotolerant community showed highest SR rates at 21 degrees C and a second optimum was found at 54 degrees C. Since pasteurization of the sediment did not affect thermophilic SR we concluded that the bacteria responsible were most likely spore-formers. The instantaneous increase in concentrations of volatile fatty acids after sediment heating to 50 degrees C indicated that thermophilic fermentative bacteria, most likely spore formers, were also present.