TNT from WWI submarine wrecks leaking into North Sea food chain

TNT residues from World War I weaponry are leaking into the North Sea, infiltrating the marine food chain more than a century after the conflict ended. Researchers discovered traces of the explosive in the water, seabed sediments, and living organisms surrounding the wreck of a German submarine.

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Sunken submarine of 1917

The study focused on the UC-30, a submarine that sank in April 1917 near the Danish island of Rømø after striking a British mine. The vessel carried 18 mines and six torpedoes. As part of the NorthSeaWrecks project, Professor Katrine Jul Andresen from Aarhus University and Danish Navy divers collected samples of water, soil, and specimens of starfish and mussels living directly on the wreckage.

Chemical analysis confirmed the presence of TNT in the animals' tissues and the immediate environment. While the current contamination is localized, the researchers warn that toxins will leak at an accelerating rate as the submarine's hull disintegrates and the munitions corrode.

Biologist Andrey Voroshilov explains that organisms like mussels act as natural filters, absorbing substances from the water. Finding TNT in their tissues proves that toxins have moved from inanimate cargo into the biological food web.

A Legacy of Underwater Hazards

The scale of the problem in Danish waters is significant. A 2024 report by Andresen for the Danish Environmental Protection Agency identifies 10,127 shipwrecks in the country's territorial waters, with approximately 15% dating back to the two World Wars. This risk is compounded by the estimated 190,000 mines deployed in the North Sea during World War I alone.

However, cleaning the seabed is not a simple task. Detonating munitions underwater to neutralize them can cause a sudden, massive release of toxins—potentially more damaging than a slow leak—depending on sea currents and seabed topography.

To address this, the REMARCO project is developing less invasive recovery methods. These include the use of crawler robots designed to pinpoint and extract hazardous objects with minimal environmental disruption.

The findings confirm that historical wrecks remain active sources of pollution after 100 years. The primary remaining question is how far these toxins spread from the crash sites. Future efforts must prioritize which objects pose the greatest threat and require extraction, and which, such as those buried deep in sand, can safely remain on the ocean floor.