WW2 shipwrecks found to be leaking pollutants that impact marine environments

The researchers from Ghent University found that the seabed of the North Sea is covered in thousands of ship and aircraft wrecks, warfare agents, and millions of tons of conventional munition such as shells and bombs.

The wrecks typically contain hazardous substances that may harm the marine environment. Yet there is a lack of information about the location of the wrecks and the effect they might have on the environment.

The hazardous chemicals emanating from one shipwreck on which the research team conducted their experiments were found to be influencing the marine microbiology around it and having a negative effect on the nearby environment.

“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,” said PhD candidate Josefien Van Landuyt.

For example, it is estimated that World War I and II shipwrecks around the world collectively contain between 2.5m and 20.4m tons of petroleum products.

“While wrecks can function as artificial reefs and have tremendous human story-telling value, we should not forget that they can be dangerous, human-made objects which were unintentionally introduced into a natural environment,” Van Landuyt continued. “Today, new shipwrecks are removed for this exact reason.”

As part of the ‘North Sea Wrecks’ project, the researchers investigated how the World War II shipwreck V-1302 John Mahn in the Belgian part of the North Sea is impacting the microbiome and geochemistry in its surrounding seabed.

“We wanted to see if old shipwrecks in our part of the sea (Belgium) were still shaping the local microbial communities and if they were still affecting the surrounding sediment. This microbial analysis is unique within the project,” Van Landuyt said.

The V-1302 John Mahn was a German fishing trawler that was requisitioned during World War II to use as a patrol boat. In 1942, during the ‘Channel Dash’, it was attacked by the British Royal Air Force in front of the Belgian coast, where it quickly sank to the bottom of the sea.

To analyse the bio- and geochemistry around the shipwreck, the researchers took steel hull and sediment samples from and around it, at an increasing distance from it and in different directions.

They found varying degrees of concentrations of toxic pollutants depending on the distance from the shipwreck. Most notably, they found heavy metals such as nickel and copper, polycyclic aromatic hydrocarbons (PAH) which occur naturally in coal, crude oil, and gasoline, arsenic, and explosive compounds.

The highest metal concentrations were found in the sample closest to the ship’s coal bunker. The freshly deposited sediment in the wake of the wreck had a high metal content. The highest PAH concentrations were closest to the ship.

“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,” explained Van Landuyt.

“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.”

The researchers also found that the ship influenced the microbiome around it. Known PAH-degrading microbes such as rhodobacteraceae and chromatiaceae were found in samples with the highest pollutant content. Moreover, sulfate reducing bacteria (such as desulfobulbia) were present in the hull samples, likely leading to the corrosion of the steel hull.

“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 concluded.