Are war wrecks and their munition cargo posing health risks to fish? – A multi-biomarker assessment of dabs (Limanda limanda) living at wreck sites in the southern North Sea

European marine waters were the scene of many sea battles and war events throughout the two World Wars, during which a high number of ships were sunk. The German Maritime Museum in Bremerhaven suspects that there are still approx. 680 wrecks from the two World Wars in the North Sea alone, many of which were partially or fully loaded with munition by the time of the sinking. The increasing corrosion of munition shells in the saline environment leads to increased leakage of chemical substances into the marine ecosystem posing risks to marine organisms, because the chemicals preserved in the munitions are toxic and classified as CMR substances (carcinogenic, mutagenic, toxic for reproduction). Particularly, the 2,4,6 - trinitrotoluene (TNT) is of great concern here, since it has been the most commonly used explosive during the World Wars.

To investigate the biological effects of the dumped ammunition on marine organisms, field studies were conducted on selected wrecks (UC30, SMS Mainz, and SMS Ariadne) from the First World War in the southern North Sea. Therefore, non-migratory dabs (Limanda limanda) were caught as close as possible to the wreck sites and investigated using a multi-biomarker approach. The dabs were first examined for obvious diseases before being dissected for subsequent assessment of relevant tissues.

First preliminary results show a significantly increased incidence of liver diseases including tumors in the dab fished at the wreck sites, compared to the fish caught at a reference area (Borkum Reef) most probably free of munition remains. Up to 65% of the examined dab (SMS Ariadne) showed at least one nodule in their liver. These results correlate with the TNT concentrations detected in the surrounding waters of the wreck site suggesting that wrecks are a point source for dissolved explosives having negative impacts on exposed marine organisms, including fish.