Transport Methan-oxidierender Mikroorganismen aus dem Sediment in die Wassersäule über Gasblasen (Bubble Shuttle)
Final Report Abstract
In a joint multidisciplinary project together with the IOW, GEOMAR and UCSB field studies were conducted in the Coil Oil Point seep area (California, USA) to investigate our hypothesis that methane oxidizing microbes (aerobic methaneoxidizing bacteria, MOB; anaerobic methane oxidizing archaea, ANME) are transported by gas bubbles from the sediment into the water column. Our studies were carried out at the Rostocker Seep site close to the Brian Seep area and combined gas bubble size measurements with gas chemistry and molecular biological studies on water column and sediment samples. Gas measurements including methane concentration and C/12C ratio show that the methane distribution pattern in the surrounding of the Rostocker Seep is strongly influenced by methane seepage and that the surface waters in this region are strongly oversaturated in methane in respect to the atmospheric equilibrium. CARD FISH analyzes were performed to describe the abundance of microbes involved in the turnover of methane in the sediment and water column. In our study site MOB could be detected in the sediment and the water column, whereas ANME-2 organisms could exclusively be detected in the sediment. The newly developed key device of the project was the so called Bubble Catcher (BC) used to collect naturally emanating gas bubbles at the sea floor together with particles attached to the bubble surface rim. BC experiments were carried out directly on a seep hole and on a reference site that was designed to trap artificial gas bubbles, which have not been in contact with the sediment. These experiments clearly show that, in contrast to ANME-2, MOB are transported by gas bubbles into the water column.
