Bentho-pelagic transport of methanotrophic microorganisms by gas bubbles

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Gas bubble releasing seep sites are relevant methane sources in aquatic systems. In the vicinity of these sites, methanotrophic microorganisms in the sediment and water column play a key role in controlling the methane flux into the atmosphere. Recent studies in the water column surrounding hydrocarbon seeps indicated an elevated abundance and activity of methanotrophic microorganisms in the near field of gas bubble plumes. During our pilot studies conducted at the Coal Oil Point Seep region in California (DFG project Transport of methane oxidizing microorganisms from the sediment into the water column (Bubble Shuttle), we could show for the first time that methanotrophic bacteria were transported by gas bubbles from the sediment into the water column. The fundamental goal of our follow-up project is to evaluate the importance of such a transport mechanism on the pelagic methane turnover at these seep sites. Multidisciplinary studies at different seep locations located in the Coal Oil Point seep field and the North Sea will help us to discuss the different environmental factors, which control the transport efficiency of the bentho-pelagic gas bubble mediated exchange process. By integrating lab-based incubation experiments we will study the activity of seep-associated benthic methanotrophic bacteria in the pelagic environment. Additional molecular biological analyses will be used to test our hypothesis that the gas bubble transport mechanism impacts the diversity of pelagic methanotrophic bacteria at seep sites. Field studies at a Blowout location in the North Sea and the integration of oceanographic measurements and models will be used to establish a budget for pelagic methanotrophic bacteria in the near field of seep sites. Overall, this approach will help us to discuss the impact of the bubble transport mechanism on the abundance of methanotrophic bacteria and the pelagic methane sink.