Since September 26, 2022 and the explosion of the Nord Stream gas pipelines, linking Russia to Germany in the Baltic Sea, Swedish, Danish and German police have been investigating to try to identify those responsible for the sabotage. At the same time, another type of investigation takes place. All around the Baltic, scientists are trying to assess the environmental consequences of the detonations, which pierced pipes in four places.
If the risk of a “climate bomb”, caused by the escape into the atmosphere of at least 70,000 tonnes of methane – a powerful greenhouse gas – was quickly ruled out by the Atomic Energy Commission and to Alternative Energies (CEA), fears remain about the impact of this incident on the ecosystem of the world’s youngest sea, already strained by pollution and climate change.
“We could see a cumulative effect, with consequences much greater than those initially anticipated”, summarizes Thomas Dahlgren, marine biologist at the University of Gothenburg, Sweden. Until January 5, for four months, he and his colleagues tracked down traces of methane in the water, using an underwater robot. The first days after the explosion, the levels were a thousand times higher than those usually observed.
“Toxic effect on fish”
Over the weeks, the methane concentration decreased, to approach normal after a few months, except in a few pockets, where the quantities remain high, as well as near the holes caused by the detonations, “which makes us think that gas continues to escape from the gas pipelines”says Thomas Dahlgren.
The high concentration of methane in the water could have several consequences. “In its dissolved form, by feeding bacteria, methane could enter the food chain and participate in eutrophication. [prolifération d’algues] of the Baltic Sea », according to the biologist. Moreover, combined with the lack of oxygen that prevails in the semi-enclosed sea, the gas could have “a toxic effect on fish”completes Mr. Dahlgren.
Published at the end of January, the results of the analyzes carried out by the Swedish Veterinary Institute (SVA), on around thirty cod, sampled in mid-October 13 km from the site of one of the explosions, seem to go in this direction. Scientists have indeed discovered an alteration of the gills of fish. “The gill filaments, i.e. the oxygen-absorbing parts, have changed shape”explains Charlotte Axen, chief veterinarian. “It affects the fish’s ability to take in oxygen and get rid of CO2 »she says.
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