A German fishing vessel that sank during World War II has been leaking pollutants that are changing the surrounding marine environment in the North Sea, according to a new study.
The 80-year-old shipwreck is the V-1302 John Mahn, a fishing trawler that was used as a German patrol boat in WWII. The British Royal Air Force bombed the vessel in 1942 and the ship capsized off the Belgian coast.
The new study, published Tuesday in the journal Frontiers in Marine Science, found toxic pollutants such as arsenic and explosive compounds in sediment samples gathered from the ocean floor near the wreck. Corroding microbes were also present in samples taken from the ship's hull.
Even after eight decades, those chemicals and microbes are affecting the "surrounding sediment chemistry and microbial ecology," the researchers wrote in the study. The results hint at the long-term environmental impacts of shipwrecks in the North Sea and around the world.
"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," Josefien Van Landuyt, one of the study's co-authors and a Ph.D. candidate studying marine biodegradation at Ghent University in Belgium, said in a statement.
In the samples with the highest concentrations of pollutants, Van Landuyt and her colleagues found microbes known to degrade chemicals called polycyclic aromatic hydrocarbons, which occur naturally in coal, crude oil and gasoline. Corroding bacteria were also detected in samples from the ship's steel hull.
Those findings suggest that the shipwreck itself, as well as the pollutants leaking from the vessel, "drive at least part of the bacterial community structure in the surrounding sediment," the researchers wrote in the study.
The pollutants found in samples from the ocean floor included various heavy metals, including nickel and copper. The highest concentrations of hazardous compounds were found closest to the sunken vessel.
The results indicate that the impact of shipwrecks on marine environments is not fully understood, especially in cases where the precise locations of sunken ships laden with munitions and petroleum are not even known.
"Although we don't see these old shipwrecks, and many of us don't know where they are, they can still be polluting our marine ecosystem," Van Landuyt said in the statement. "In fact, their advancing age might increase the environmental risk due to corrosion, which is opening up previously enclosed spaces. As such, their environmental impact is still evolving."
It's estimated that wrecks from WWI and WWII around the world collectively contain as much as 20.4 million tons of petroleum products, according to the researchers.
The V-1302 John Mahn research is part of an initiative called the North Sea Wrecks project, which is studying the seabeds around shipwrecks off the Belgian coast.
"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," Van Landuyt said, "and are still making an impact, leaching chemicals, fossil fuels, heavy metals from — sometimes century old — wrecks we don't even remember are there."