There are underwater ticking time bombs in the North and Baltic seas—both literally and figuratively.
In the straightforward sense, actual bombs litter the ocean waters along the coast of Germany. Nearly 1.3 million metric tons of conventional munitions, including shells, rockets, torpedoes, and more, sit unexploded in the North Sea, and an additional 300,000 tons of weapons and 30,000 tons of chemical warfare agents (CWA) pollute the nearby Baltic Sea. It’s a result of a violent and rather hastily-executed disarmament that the Allied powers forced upon Germany following World War II, along with other shipwrecks and battles from both World Wars.
And then there’s the other volatile “bomb” that researchers claim could be the even bigger danger in the European waters: These munition-polluted oceans are causing some serious harm to marine ecosystems.
The environmental concerns caused by the dumping of World War weaponry decades ago is the crux of this Popular Mechanics feature. While the unexploded munitions scattering the German coastline certainly pose a threat to humans and boats who unexpectedly stumble in their path, it’s the more invisible danger within the North and Baltic sea ecosystems that could be much more lethal.
To understand the pollution crisis, you first have to look at the dangerous chemicals at the root of the problem. All of the bombs, torpedoes, and other artillery dispersed in the North and Baltic seas sit concealed in the seabed, leaching toxic remnants into the ocean waters as their casings degrade. Research conducted conducted in the North Sea by North Sea Wrecks (NSW) between 2018 and 2023 confirmed the presence of toxic byproducts of munitions, like trinitrotoluene (TNT), in sediment and marine life near shipwrecks and weapons dump sites.
In the middle of these weapons graveyards in the North and Baltic seas live rich, diverse marine wildlife—but the scale of pollutants permeating the water is putting those organisms in harm’s way. One animal in particular provides the best evidence of this: flatfish. Scientists have uncovered alarming traces of TNT and its metabolites in the muscle tissues of fish living near North Sea unexploded ordnance (UXO), with recorded concentrations of up to 4 nanograms per gram (ng/g).
As detailed in the full Pop Mech feature, writer Stav Dimitropoulos witnessed scientific analysis of these sick fish first-hand, watching aboard research ship Heincke as experts from the Alfred Wegener Institute for Polar and Marine Research (AWI) caught and examined flatfish from the North Sea riddled with pink-colored lumps on their tissues—a sign of cancer.
Back on Heincke, in one of its labs, AWI scientists dissected the still-living fish and removed the intestines. They quickly placed samples, including specimens of bile, liver, fillet, and kidneys, in liquid nitrogen to preserve them for later gene and protein analysis. Among the flatfish caught by the Heincke researchers were common dabs (Limanda limanda), which are found in the sandy and muddy seabeds of the North Sea and the Baltic. This species, often a staple in European coastal cuisines, is prized for its delicate texture and mild flavor and rarely grows longer than 20 centimeters. The team found the common dabs’ tissue dotted with small nodules of a sickly pinkish color. These are indicative of cancer in the fish, [marine biologist Matthias] Brenner said.
But it’s not just cancer that’s plaguing the North and Baltic sea fish. Following the AWI ocean expedition at the heart of the Pop Mech feature, further lab tests on water, sediment, and tissue samples gathered at the site of the Imperial German Navy’s sunken, World War I-era SMS Ariadne found that fish near the vessel had signs of liver disease tied to TNT contamination. The more TNT present in the ocean, researchers discovered, the more deaths in a given fish population.
And what does that mean for all of those fish caught along the Germany coastline that then make their way onto our own dinner plates? It’s challenging for experts to definitively link health impacts, particular pollutants, and people’s diets, especially considering the vast number of harmful materials that have permeated food production (like microplastics, pesticides, lead, and many other toxic substances). But the numbers don’t lie—the high concentrations of UXO residues found in fish has researchers concerned. There’s no established and accepted “safe” level for materials like TNT in seafood, but that doesn’t necessarily mean it’s ideal for humans to consume.
Now, the push goes on to defuse the environmental bomb kickstarted during the World Wars nearly 100 years ago. Scientists continue to innovate new weapon-eliminating technologies (including robots)—but it could take hundreds of years to effectively mitigate the marine crisis in the North and Baltic seas.