In 2024, a Second World War munitions dumpsite was found at the bottom of Lübeck Bay, a large inlet in the Baltic Sea straddling the northern shoreline of Germany.
Scientists from the Shirshov Institute of Oceanology (SIO) found that the debris, identified as warheads from Nazi Germany’s V-1 flying bombs, was releasing high levels of toxic chemicals into the surrounding water.
It therefore came as quite a surprise when the team discovered vast numbers of animals living on the abandoned explosives – in fact, the scientists recorded more marine life on the munitions than on the sediment around them.
Published in the journal Communications Earth & Environment, the research suggests that the hard metal casings of the bombs provide valuable habitat for thousands of organisms that appear to outweigh the risks of chemical exposure.
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Explosive habitat
Before the London Convention on the Prevention of Marine Pollution in 1972, it was common practice to dispose of unused munitions by dumping them at sea. But these old explosives can be toxic.
Water and sediment samples taken at the Lübeck Bay site revealed that levels of explosive compounds such as TNT and RDX in the water varied from as little as 30 nanograms per litre to as much as 2.7 milligrams per litre – high enough to be fatal to marine life.
Yet despite this toxic danger, the old munitions appear to be providing solid, animal-friendly habitat in areas otherwise dominated by soft sediment.
To find out exactly how beneficial the debris is as a marine habitat, SIO researchers used a remotely operated submersible to help record the number of animals at the site. They found that the abandoned weapons hosted an average of 43,000 organisms per square metre – including crabs, starfish and fish – compared with just 8,200 on surrounding seabed sediment.
The benefits of living on a hard surface therefore appear to outweigh the risks of chemical exposure, say the authors.
What next?
Although the munitions are currently an important habitat in the bay, the study suggests replacing them with a safe artificial surface would further benefit the local ecosystem. The authors also note that most organisms were found on the metal casings rather than exposed explosives, suggesting life forms may be trying to reduce their contact with toxic material.
Another study published in Scientific Data reveals a similar story across the Atlantic at the so-called 'Ghost Fleet' at Mallows Bay in Maryland, US. Here, researchers analysed 147 shipwrecks, all built during World War I and deliberately sunk in the 1920s. They found the wrecks teeming with life, the sunken debris providing food and shelter for numerous species including ospreys and Atlantic sturgeon.
Top image: Second World War munitions in Baltic Sea. Credit: GEOMAR
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