Acoustic characterisation of unexploded ordnance disposal in the North Sea using high order detonations

Current species protection does not serve its porpoise-Knowledge gaps on the impact of pressures on the Critically Endangered Baltic Proper harbour porpoise population, and future recommendations for its protection

Successful management requires information on pressures that threaten a species and areas where conservation actions are needed. The Baltic Proper harbour porpoise population was first listed as Critically Endangered by the International Union for the Conservation of Nature in 2008. Now, 16 years later, there is no change in conservation status despite ample conservation policy calling for its protection and an urgent need for management action to protect this population. Here, we provide an overview of the current status of the population, highlight knowledge gaps on the impact of pressures, and make recommendations for management of anthropogenic activities. Based on an exceeded limit for anthropogenic mortality, the high concentrations of contaminants in the Baltic Sea, combined with reductions in prey availability and increases in underwater noise, it is inferred that this population is likely still decreasing in size and conservation action becomes more urgent. As bycatch and unprotected underwater explosions result in direct mortality, they must be reduced to zero. Inputs of contaminants, waste, and existing and emerging noise sources should be minimised and regulated. Additionally, ecosystem-based sustainable management of fisheries is paramount in order to ensure prey availability, and maintain a healthy Baltic Sea. Stranding networks to routinely assess individuals for genetic population assignment and health need to be expanded, to identify rare samples from this population. Knowledge is still scarce on the population-level impact of each threat, along with the cumulative impact of multiple pressures on the population. However, the current knowledge and management instruments are sufficient to apply effective protection for the population now. While bycatch is the main pressure impacting this population, urgent conservation action is needed across all anthropogenic activities. Extinction of the Baltic Proper harbour porpoise population is a choice: decision-makers have the fate of this genetically and biologically distinct marine mammal population in their hands.

In-situ comparison of high-order detonations and low-order deflagration methodologies for underwater unexploded ordnance (UXO) disposal

The unexploded ordnance (UXO) on the seabed off Northwest Europe poses a hazard to offshore developments such as windfarms. The traditional removal method is through high-order detonation of a donor explosive charge placed adjacent to the UXO, which poses a risk of injury or death to marine mammals and other fauna from the high sound levels produced and is destructive to the seabed. This paper describes a sea-trial in the Danish Great Belt to compare the sound produced by high-order detonations with that produced by deflagration, a low-order disposal method that offers reduced environmental impact from noise. The results demonstrate a substantial reduction over high-order detonation, with the peak sound pressure level and sound exposure level being around 20 dB lower for the deflagration. The damage to the seabed was also considerably reduced for deflagration, although there was some evidence for residues of explosives related chemicals in sediments.

Ecotoxicological Risk of World War Relic Munitions in the Sea after Low- and High-Order Blast-in-Place Operations

Submerged munitions from World War I and II are threatening human activities in the oceans, including fisheries and shipping or the construction of pipelines and offshore facilities. To avoid unforeseen explosions, remotely controlled "blast-in-place" (BiP) operations are a common practice worldwide. However, after underwater BiP detonations, the toxic and carcinogenic energetic compounds (ECs) will not completely combust but rather distribute within the marine ecosphere. To shed light on this question, two comparable World War II mines in Denmark's Sejerø Bay (Baltic Sea) were blown up by either low-order or high-order BiP operations by the Royal Danish Navy. Water and sediment samples were taken before and immediately after the respective BiP operation and analyzed for the presence of ECs with sensitive GC-MS/MS and LC-MS/MS technology. EC concentrations increased after high-order BiP detonations up to 353 ng/L and 175 μg/kg in water and sediment, respectively, while low-order BiP detonations resulted in EC water and sediment concentrations up to 1,000,000 ng/L (1 mg/L) and >10,000,000 μg/kg (>10 g/kg), respectively. Our studies provide unequivocal evidence that BiP operations in general lead to a significant increase of contamination of the marine environment and ecotoxicological risk with toxic ECs. Moreover, as compared to high-order BiP detonations, low-order BiP detonations resulted in a several 1000-fold higher burden on the marine environment.

Environmental impact of the explosion of the Nord Stream pipelines

Armed conflicts have, in addition to severe impacts on human lives and infrastructure, also impacts on the environment, which needs to be assessed and documented. On September the 26th 2022, unknown perpetrators deliberately ruptured the two gas pipelines Nord Stream 1 and 2 with four coordinated explosions near a major chemical munition dump site near the Danish island of Bornholm in the Baltic Sea. While the massive release of natural gas into atmosphere raised serious concerns concerning the contribution to climate change-this paper assesses the overlooked direct impact of the explosions on the marine ecosystem. Seals and porpoises within a radius of four km would be at high risk of being killed by the shockwave, while temporary impact on hearing would be expected up to 50 km away. As the Baltic Proper population of harbour porpoises (Phocoena phocoena) is critically endangered, the loss or serious injury of even a single individual is considered a significant impact on the population. The rupture moreover resulted in the resuspension of 250000 metric tons of heavily contaminated sediment from deep-sea sedimentary basin for over a week, resulting in unacceptable toxicological risks towards fish and other biota in 11 km3 water in the area for more than a month.