Department Surface Waters - Research and Management

Methane oxidation in low-oxygen zones

Context

Lakes release a large amount of methane into the atmosphere, even though they only cover a few percent of Earth’s surface. It is estimated that lakes account for up to 16 % of the total atmospheric methane emissions, but there are still many uncertainties. Certain microorganisms, called methanotrophs, are able to oxidize methane to carbon dioxide and thus help control the amount of methane which is released into the atmosphere.

Aims

Many open questions remain about if and how microorganisms convert methane to carbon dioxide in oxygen free zones of lakes. Therefore, our investigations focus on stratified lake systems, where waters are oxygen free below a certain depth. We are interested in finding out which microorganisms are oxidizing methane in the low-oxygen and anoxic zones of lakes, how fast they do this and what other living requirements they have.

Approaches

In order to answer these questions we study a variety of different lakes: Rotsee (Switzerland), Lake Zug (Switzerland), Lake Kivu (Ruanda), Lake La Cruz (Spain) and Lake Powell (Canada). We take high resolution profiles of relevant physical and chemical parameters. Furthermore, we take water samples from interesting depths and perform a variety of experiments to determine methane consumption rates and which microorganisms are involved.

Methanotroph cells found in Rotsee, Switzerland, visualized by CARD-FISH (catalyzed reporter deposition in-situ hybridization) along with their carbon assimilation activity measured by nanoSIMS (nano-scale secondary ion mass spectrometry).