BIOGEOCHEMICAL ACTIVITY OF ANAEROBIC MICROORGANISMS FROM BURIED PERMAFROST SEDIMENTS

Permafrost sediment samples, ranging in age from 7 thousand to 2 milli on years, from the northeastern region of Russian Arctic were analyzed for evidence of reducing conditions, viable populations of anaerobic bacteria and their metabolic endproducts. Field analyses of samples sh owed that all sediments were reduced with a redox potential ranging fr om +40 to -256 mV. Ferrous iron, acid-soluble sulfide, and methane wer e detected in the frozen sediments. Direct bacterial counts were! 10(7 ) to 10(8) cells/g sediments as determined by epifluorescence microsco py using acridine orange. Denitrifiers and (H-2 + CO2)-utilizing metha nogens were detected in all samples, and acetoclastic methanogens, sul fate reducers, and Fe(III) reducers were detected in some samples and at much lower numbers. [S-35]Sulfide production from [S-35]sulfate was detected in soils incubated anaerobically at 4 degrees C for 6 months . Thus anaerobic metabolic activity was present at temperatures near f reezing. These results suggest that viable anaerobic bacteria reside i n aged, reduced permafrost sediments. Future investigation should focu s on detecting activity in the frozen state.