UK - North Sea wrecks: Toxic legacies of war. Investigating abandoned munitions on the seabed.

Until recently, the environmental impact of these wrecks was largely unknown and, as far as the presence of munitions is concerned, they represented a true Pandora’s box.

The North Sea Wrecks project has changed this. Researchers examined the munitions and the possible release of toxic substances from a few selected wrecks in the North Sea. Are these wrecks really leaving us with a toxic legacy of war, or are we worrying about nothing? In this article, we try to discover the answer.

On 11 February 1942, with World War II showing no sign of abating, German naval forces launched a risky operation in the English Channel. The battleships Scharnhorst and Gneisenau and the heavy cruiser Prinz Eugen needed to return from the French port of Brest to their German home ports as soon as possible. They were to be assisted in this by numerous escort ships. The riskiest but shortest route was through the sea strait between England and France, and the Germans decided to take their chances. On 13 February, they managed to pilot the ships – not entirely unscathed – into German waters: a successful military operation that came to be known as Operation Cerberus, or the Channel Dash.

What the history books fail to report, however, is that one of the escort ships fared less well. In the afternoon of 12 February, six British Air Force bombers took the German patrol boat V-1302 John Mahn under fire off the coast of Ostend. The first bomb struck the vessel midships and exploded in the boiler room. The second, fatal, bomb hit the stern tube and sank the John Mahn in barely half a minute. Although 27 crew members were rescued by other patrol boats and vessels of the 2nd Mine Sweeper Flotilla, 11 sailors were missing and presumed dead.

Unknown environmental impact

The wreck of the John Mahn still lies some 35 metres down on the bottom of the Belgian part of the North Sea. Apart from the missing superstructure and a large crack on the port side, the wreck is largely intact. The John Mahn is just one of many ships to have met such an inglorious end, as it is estimated that there are some 290 shipwrecks on the Belgian North Sea floor, many of them silent witnesses to the two world wars. However, the cultural heritage value of these shipwrecks and the stories of human suffering that they represent mean that many of them still arouse fascination, decades later.

Less well known are the locations, identities and conditions of these shipwrecks, along with their negative environmental impacts due to the oil, lubricants, paints, fire extinguishing materials, metals, bombs and cargo left in them. Up to now, we have only been able to guess at the effect of these on fauna and flora.

Oil pollution is one well-studied environmental issue, with examples such as the wreck of the US battleship Arizona at the bottom of Pearl Harbor in Hawaii, which is still leaking oil since sinking in World War II, 82 years ago. Other wrecks may not leak oil straight away, but come to do so in time due to corrosion of the oil tanks on board. While pumping the oil out of shipwrecks can avoid such unpleasant surprises, it is a costly operation and there are simply too many wrecks for this to be a feasible option: 8,569 potentially polluting wrecks lie on the seabed worldwide. Together, these wrecks are estimated to contain between 2.5 and 20.4 million tons of oil. To give an idea of what this means, it is about 2 to 20 times the amount of oil that was released during the Deepwater Horizon drilling rig disaster in the Gulf of Mexico in 2010 (about 1.1 million tons of leaked oil).

As well as oil, sunken ships can contain coal, lubricants, anti-fouling paint and other chemicals needed for ship operations, as well as hazardous cargo. The most well-known example of the latter is that of submarine U-864, which attempted to smuggle a cargo of 67 tons of mercury from Germany to Japan. The submarine was sunk on 9 February 1945 near Bergen in Norway, where it now lies at the bottom of a 150-metre-deep fjord. It is impossible to remove the mercury on board due to the submarine’s position on the edge of the continental slope, as disrupting the wreck could worsen the problem rather than fix it, which of course needs to be avoided at all costs.

Finally, there is the issue of war munition. Almost all war wrecks have munition on board to a greater or lesser extent, but what is its condition? How much munition is left on board? Is it still dangerous and is it leaking? And, how can we best deal with these wrecks and their toxic cargoes? These are all questions that, until recently, there were no answers to. Answers needed to be found, however, especially considering the blue economy activities currently being developed in the North Sea (e.g. wind farms, aquaculture, coastal defence). A transnational approach was therefore needed.

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