Over twenty marine protected areas affected by the Nord Stream leak

Methane from the exploded Nord Stream pipeline has spread to large parts of the southern Baltic Sea. Over 20 marine protected areas are affected. This is shown by a new study.

– How long the methane stayed in the sea and how far it was able to spread was quite striking to me, says Bastien Queste, associate professor in oceanography and co-author of the study. 

It was in September 2022 that the Nord Stream gas pipeline exploded at the bottom of the Baltic Sea, east of Bornholm. The methane gas that leaked out caused elevated levels of methane in the atmosphere. But now, a new study published in the scientific journal Nature Communications shows that the gas also spread into large parts of the waters of the southern Baltic Sea and stayed there for several months. 

– I expected that much of the methane would have been consumed by bacteria or escaped to the atmosphere. But when we came back to the site of the leak much later, we were still seeing very high concentrations, which was quite surprising, says Bastien Queste. 

Underwater robot provided answers

The study was a collaboration between the University of Gothenburg and the Voice of the Ocean research foundation (VOTO). To get a detailed picture of how the gas was dispersed, they used an underwater robot, a so-called glider, which could measure methane levels from the surface to the depths. 

– Gliders are great for this kind of study. They can swim, which means we can send them wherever we want, says Bastien Queste. The survey found that methane levels were up to 1000 times above normal just after the pipeline explosion. But in some areas, abnormally high concentrations were measured several months afterwards. 

Marine protected areas affected

Using the measurements, the researchers were also able to model how the methane spread through the water. This showed that over 14 percent of the entire Baltic Sea was exposed to methane levels at least five times above normal. In addition, ocean currents had transported the methane to 23 marine protected areas. But unlike oil spills, it is not possible to recover the leaked methane from the sea, says Bastien Queste. 

– Marine protected areas exist because they represent unique or important aspects of the ecosystem. So, it is worrying when pollution spreads to these areas, but also to realize how powerless we are to deal with it. 

The next step will be for someone to investigate whether the methane leak may have affected marine organisms.