An 80-year-old shipwreck from World War II is still influencing the ocean floor’s microbiology and geochemistry.

Scientists have found that a World War II wreckage, after being submerged in the ocean for 80 years, continues to affect the local marine ecosystem and chemical composition of the seafloor.

They explain in the journal Frontiers in Marine Science how the shipwreck is contaminating the sediment on the ocean floor of the North Sea with dangerous contaminants like explosives and heavy metals, which in turn has an effect on the marine microbiology in the area.

Thousands of ship and aircraft wrecks, warfare chemicals, and millions of tons of conventional weapons like shells and bombs are all present on the North Sea’s seafloor.

Hazardous materials found in wrecks, like explosives and petroleum, could endanger the maritime environment. However, little is known about where the wrecks are and what impact they might have on the ecology.

The public is fascinated by shipwrecks because of their historical significance, but Ghent University PhD candidate Josefien Van Landuyt says that the potential environmental impact of these wrecks is generally underestimated.

For instance, it is believed that the total amount of petroleum products found in shipwrecks from World Wars I and II worldwide ranges from 2.5 million to 20.4 million tons.

However, as Van Landuyt pointed out, we should not forget that wrecks can be dangerous, human-made items which were accidentally thrown into a natural environment and can serve as artificial reefs and have immense human story-telling value. 

“Today, new shipwrecks are removed for this exact reason.”

Van Landuyt and her coworkers looked at the effects of the World War II wreckage V-1302 John Mahn on the microbiome and geochemistry of the surrounding seabed as part of the North Sea Wrecks project. The wreck is located in the Belgian portion of the North Sea.

They wanted to find out if shipwrecks from the past were still influencing the current microbial populations and the sediment around them in the waters off Belgium. 

“This microbial analysis is unique within the project,” said Van Landuyt.

Microbes and dangerous chemicals

During World War II, the German fishing trawler V-1302 John Mahn was commandeered and converted into a patrol vessel. It was bombed by the British Royal Air Force in front of the Belgian shore during “the Channel Dash” in 1942, and it immediately fell to the bottom of the sea.

To study the biochemistry and geochemistry of the area around the shipwreck, scientists took samples of the steel hull and sediment from the shipwreck and the area around it. The samples were taken at different distances and in different directions.

Depending on how far away from the shipwreck they were, they discovered varied levels of harmful pollution concentrations. Most notably, they discovered explosive substances, polycyclic aromatic hydrocarbons (PAHs), arsenic, and heavy metals (including nickel and copper). PAHs are chemicals that naturally occur in coal, crude oil, and gasoline.

The area of the sample nearest to the ship’s coal bunker had the greatest metal contents. Fresh sediment in the wreck’s wake was high in metal. The areas nearest to the ship had the highest PAH concentrations.

Van Landuyt emphasized that even if we don’t see or know where historical shipwrecks are, they may still be damaging the maritime environment.

In reality, corrosion, which is opening up previously contained compartments, may raise the environmental risks as they age. As a result, their influence on the ecosystem is still developing.

Scientists discovered that the ship had an effect on the local microbiota. Rhodobacteraceae and Chromatiaceae, which are known to break down PAH, were found in samples with the most pollution. Additionally, sulfate-reducing bacteria (such Desulfobulbia) were found in the hull samples, which most likely caused the steel hull to rust.

Invisible polluters

Van Landuyt said that this study is just the tip of the iceberg. 

“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,” he said.

“We only investigated one ship, at one depth, in one location. To get a better overview of the total impact of shipwrecks on our North Sea, a large number of shipwrecks in various locations would have to be sampled,” Van Landuyt added.

Image Credit: Getty

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