The Big Picture: Unexploded munitions dumped in the Baltic Sea after World War II have become artificial reefs, supporting dense and diverse marine life. This discovery challenges assumptions about the environmental impacts of submerged munitions and raises questions about how to safely manage these sites.
Methodology: Researchers used a remotely operated vehicle (ROV) to examine and film nine munition objects at a previously undocumented dumpsite in the Lübeck Bay. They identified epifauna species, calculated abundance, and collected water samples near the objects to measure concentrations of explosive compounds.
The Discovery: The munitions, identified as warheads from V1 flying bombs, hosted thriving epifauna communities with densities over 43,000 individuals per square meter. Eight species were identified, dominated by Polydora ciliata polychaetes. Explosive compound concentrations in surrounding water reached potentially toxic levels of up to 2.73 mg/L for TNT.
Limitations: The study examined only one site at one point in time. Seasonal variations and comparisons with natural hard substrates in the same area were not possible due to a lack of large stones or boulders in the immediate vicinity.
The Takeaway: Dumped munitions can serve as artificial reefs, supporting abundant marine life despite the presence of toxic compounds. Future management of such sites should consider replacing munitions with safe artificial structures to maintain these newly established ecosystems.