A filter for greenhouse gas is produced in the deep sea

October 16, 2018 Marine researchers observe the settlement of a deep-sea mud volcano after an eruption

In a long-term study, ocean researchers from Bremen have succeeded in observing the colonization of a deep-sea mud volcano after an eruption for the first time. The rich life develops very slowly around the crater. The first settlers are extremely small creatures that "eat" methane that flows from the volcano. This ensures that this climate-damaging gas does not escape into the atmosphere. Gradually, more microbes and finally higher species join.

Large quantities of the greenhouse gas methane are stored in the seabed. Fortunately, only a small part of the methane reaches the atmosphere and can develop its effect as a climate-relevant gas, because it is mostly degraded in the sediment. The dismantling is done by a specialized microbial community. It manages to reduce up to 90 percent of the escaping methane. Therefore, these microbes are called the "microbial methane filter". If the greenhouse gas were to rise through the water and into the atmosphere, it could have a significant impact on our climate.

But the microbes do not work so efficiently everywhere. In areas of the seabed that are more turbulent than normal - such as gas leaks or so-called underwater volcanoes, the microbes remove just one tenth to one third of the escaping methane. What is the explanation? Emil Ruff and his colleagues from the Max Planck Institute in Bremen and the University of Bremen have dealt with this question.

Methane mining around the mud volcano

The Håkon Mosby mud volcano is located at 1,250 meters in the Norwegian North Sea. Warm mud rises from deep layers of the seafloor. In a long-term experiment, the researchers have been able to film the exit of the mud and to examine it closely. "We found significant differences in the different communities on the ground. In fresh mud that had just leaked out, we found only a few organisms. The older the mud was, the more living beings were contained in it," says Ruff. Within a few years after exiting, both the number of microorganisms and their diversity increased tenfold. The metabolic activity of the microbial community also increased significantly over time. Although methane decomposers were already present in the very young sludge, efficient filtering of the greenhouse gas is probably done only after decades.

"The study has given us new insights into these unique communities," says Ruff. "But it also shows that these habitats need to be protected. If the methane eaters continue to help remove the methane, then we must not destroy their habitats with trawling and deep-sea mining. These habitats are almost like a rainforest - they take decades to grow again after a disturbance."