Marine life thrives on World War II explosives in Baltic Sea, study finds

Scientists exploring a World War II weapons dumpsite in the Baltic Sea have documented swarms of crabs, worms, and fish living on the surfaces of long-abandoned warheads, challenging assumptions that the remnants are entirely toxic to marine life. An undersea submersible filmed life forming on top of the munitions near the Bay of Lübeck off Germany, where the wrecks are plentiful and the landscape is shaped by decades of deposition.

"We were prepared to see significantly lower numbers of all kinds of animals," said Andrey Vedenin with the Senckenberg Research Institute in Germany. "But it turned out the opposite." The study, published Thursday in the Journal of Communications Earth and Environment, shows life clustering on hard surfaces that remain after decades on the sea floor, with many warheads still containing chemical agents, explosives like TNT, and even nuclear remnants.

Researchers filmed networks of anemones, starfish, and other organisms spreading across the warheads and other hard objects, in some cases outpacing life on the surrounding seabed. The Bay of Lübeck area is off Germany's Baltic coast and hosts a concentration of munitions left over from the two world wars. The hard surfaces create anchor points in an otherwise flat, sandy, and muddy seabed, according to Andrey Vedenin.

"Normally, one does not study the ecology of bombs," said James Porter, an ecologist at the University of Georgia who was not involved with the research. The finding underscores the potential for life to adapt to highly altered, contaminated environments, even as the trade-offs, including toxin exposure, remain to be determined.

The area is also fairly isolated from ongoing human activity because of chemical contamination, creating a somewhat protective bubble for the critters to thrive despite some toxic trade-offs. Researchers are now working to calculate how much contamination underwater creatures have absorbed from the weapons and to see whether those organisms can reproduce. Germany’s waters alone hold roughly 1.6 million tons of discarded weapons, most dating to World War II and earlier conflicts.

The study aligns with earlier work showing artificial wrecks can become wildlife habitats. Marine conservation biologist David Johnston of Duke University noted that sunken World War I ships along the Potomac River have become habitats for wildlife, offering a broader view of how human-made structures shape marine life. "I think it's a really cool testimony to the strength of life," Johnston said.

The researchers caution that the presence of life on contaminated warheads does not mean these sites are safe refuges for biodiversity; instead, they illustrate resilience and the complex trade-offs in polluted oceans. The findings contribute to a growing body of work on how marine ecosystems adapt to legacy contamination and may inform future monitoring and remediation efforts.