Sign up for CNN’s Wonder Theory science newsletter. Explore the universe with news on fascinating discoveries, scientific advancements and more.
A World War II shipwreck is still leaking explosives and other toxic elements into the ocean floor of the North Sea more than 80 years after it was sunk.
The wreck’s hazardous pollutants continue to impact nearby marine microbiology, as well as the geochemistry of the seafloor, according to new research published Tuesday in the journal Frontiers in Marine Science.
“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 study author Josefien Van Landuyt, a doctoral candidate, bioengineer and microbiologist at Ghent University in Belgium.
The wreck of the V-1302 John Mahn rests in the Belgian part of the North Sea, just one of thousands of ship and aircraft wrecks located along the seabed. The ship first served as a German fishing trawler and was requisitioned by the German Navy during World War II as a patrol boat.
Six British Royal Air Force Hawker Hurricane aircraft patrolling the Belgian coast attacked the ship on February 12, 1942. Two aerial bombs struck the ship, causing it to sink rapidly. The strike claimed the lives of 11 sailors and carried the ship’s cargo — munitions and coal reserves — to the bottom of the sea.
A group of researchers began studying the potential impact of the shipwreck as part of the North Sea Wrecks project. The goal of the project is to investigate wrecks located across the North Sea seabed, according to Van Landuyt. The North Sea borders Belgium, Norway, Denmark, the Netherlands, Great Britain and Germany — all of which were involved in WWII.
The study’s researchers estimate that, across the world’s oceans, shipwrecks from both world wars contain between 2.5 million and 20.4 million metric tons of petroleum products.
She hopes the data collected by the project will help policy makers decide the best steps in dealing with the North Sea’s wrecks and protecting its ecosystem.
“The research performed within this project will be used to develop a decision-making tool to asses the potential environmental risk a war time shipwreck poses on the environment, which will hopefully contribute to a safe and healthier marine environment.”
Heavy metals and toxic chemicals
The study team collected samples from the ship’s steel hull as well as the surrounding sediment. Researchers also gathered samples at a series of increasing distances from the ship in different directions to see how far pollution stretched.
The samples revealed heavy metals such as nickel and copper as well as arsenic and explosive compounds. Polycyclic aromatic hydrocarbons, or PAHs, which are chemicals that naturally occur in gasoline, coal and crude oil, were also found.
The team uncovered the highest concentration of metals closest to the ship’s coal bunker, but it was also present in sediment that was deposited in the wake of the wreck. The samples with the most concentrated chemicals were also located close to the ship.
The wreckage has also influenced microbiology found around the ship. The team discovered Rhodobacteraceae and Chromatiaceae, microbes that degrade PAHs in sediment samples containing the most pollutants.
The sulfate-reducing bacteria Desulfobulbia was also identified in samples taken from the hull, which is likely responsible for its corrosion.
Marine impact evolves over time
Shipwrecks may become more dangerous to the environment as they age because corrosion can open up once enclosed spaces — which means their environmental impact continues to evolve, Van Landuyt said.
“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 said. “Today, new shipwrecks are removed for this exact reason.”
In addition to wrecks, the North Sea contains up to 1.6 million metric tons of ammunition like shells and bombs dumped after each world war ended.
These explosives, as well as other chemical warfare agents, can be toxic to marine life. Petroleum products are also known to impact the growth, reproduction, feeding and tissues of marine organisms, according to the study.
“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 said in a statement.
The study only contained an analysis of the V-1302 John Mahn shipwreck, but the researchers emphasized more shipwrecks in a variety of locations need to be sampled to have a better overview of their impact on the North Sea. Van Landuyt was surprised by just how many wrecks, including those that are almost intact, can be found there.
“Remediation techniques (such as removing munitions by divers, pumping out oil tanks) are available but they are challenging and expensive to attempt,” she said. “The decision-support tool enables us to focus resources.”