Methane gas accumulation and degradation in Aarhus Bay sediments (Denmark) - a case study

Microbial formation of methane gas is a common phenomenon in northern European ocean margin sediments. Only a fraction of this methane is released into the water column, while large amounts remain in the sediments and build up vast shallow gas accumulations in the Holocene mud. The retention of this gas in the Holocene is controlled by microbial anaerobic oxidation of methane which occurs in a narrow interface layer of sulfate and methane mixing termed the sulfate-methane-transition zone (SMTZ). The effectiveness of this methane barrier is well recognized, but the controlling factors for this process are only poorly understood.