This World War II Shipwreck Is Leaking Toxins Into the Ocean. Are Others Polluting the Sea, Too?

 “The general public is often quite interested in shipwrecks because of their historical value, but the potential environmental impact of these wrecks is often overlooked.”

The John Mahn has served three key purposes in its lifetime. First, the ship operated as a fishing trawler. Then, During World War II, Germany turned it into a patrol boat that British aircraft would eventually attack and sink. Since then, the John Mahn has spent the last 80 years impacting the microbiology and geochemistry of the ocean floor in the North Sea; Now, it’s giving scientists a rare opportunity to study how old shipwrecks could pollute the deep sea.

In a new study published earlier this month in the journal Frontiers in Marine Science, a research team from Ghent University, the Museum of Natural Sciences of Belgium, and the Flanders Marine Institute examined samples from the ship’s hull and nearby sediment. They found that hazardous materials from John Mahn’s onboard explosives, coal bunker, and corroding steel frame have been “[significantly steering] the surrounding sediment chemistry and microbial ecology,” the authors write in the papers abstract.

Moreover, these results raise questions about other shipwrecks rusting away at the bottom of the sea—the United Nations estimates that there are about three million total wrecks—and what we should do about them. The North Sea alone is littered with countless other ship and aircraft wrecks, as well as warfare agents and “millions of tons of conventional munition such as shells and bombs,” according to a press release.

John Mahn on the Seas

Before the John Mahn served as a patrol boat for the Germans, it was given the fishery identification number BX 221. That lasted from September 1932 until 1939, when it became part of the 13th Outpost Boat Flotilla, known as Vorpostenflottille 1302.

During the 1942 Channel Dash, a German naval operation, the British Royal Air Force attacked the ship near the Belgian coast. Flotilla 1302 combined with the Vp 1303 during Operation Cerberus, an attempt to help three German battleships—ScharnhortsGneisenau, and Prinz Eugen—break through the English Channel into the North Sea for added protection back to German-occupied Norway.

During the operation, 242 British aircraft, the largest daylight Bomber Command operation of the war at that time, attacked Vp 1302. While the three German battleships were able to get by largely unscathed, two aerial bombs hit the John Mahn. It immediately sunk and 12 crew members died in the attack.

The Environmental Impact of Shipwrecks

“The general public is often quite interested in shipwrecks because of their historical value,” Josefien Van Landuyt, a Ph.D. candidate at Ghent University in Belgium, and one of the study’s authors, says in the news release, “but the potential environmental impact of these wrecks is often overlooked.”

For example, estimates state that World War I and World War II shipwrecks collectively contain up to 20 million tons of petroleum products, per the release. “While wrecks can function as artificial reefs and have tremendous human storytelling value, we should not forget that they can be dangerous, human-made objects which were unintentionally introduced into a natural environment,” Van Landuyt says. “Today, new shipwrecks are removed for this exact reason.”

As part of the North Sea Wrecks project that looks at the toxic legacies of war, Van Landuyt and colleagues specifically investigated the John Mahn wreck in the Belgian portion of the North Sea, seeing how it is shaping the local microbial communities and if it was still having an impact on the surrounding sediment.

Scientists found varying degrees and concentrations of toxic pollutants including heavy metals such as nickel and copper; polycyclic aromatic hydrocarbons; arsenic; and explosive compounds. In other words, the team found the ship did influence the microbiome around it.

“People often forget that below the sea surface, we humans have already made quite an impact on the local animals, microbes, and plants living there and are still making an impact, leaching chemicals, fossil fuels, heavy metals from—sometimes century old—wrecks we don’t even remember are there,” Van Landuyt says. “We only investigated one ship, at one depth, in one location.”

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