Search

Contemporary society’s perception of past wars is almost exclusively driven by historic sources such as film recordings, photographs and written documents that are presented in mass media. However, the legacy of these wars is still present throughout European soil and waters, including the Baltic Sea. The marine waters of every Baltic Sea state contain warfare materials. Resulting risks may be direct and short-term. Fishermen, divers, offshore wind farm constructors and beachgoers can potentially be exposed to their remains while performing their daily work or while collecting objects in the surf. Other potential effects might be indirect and long-term such as the accumulation of carcinogenic toxic substances and their metabolites in the marine food web. Since 1974 Contracting Parties of the Helsinki Convention are seeking to address the increasing environmental challenges from human activities and that were having a severe impact on the marine environment. This includes the protection of the Baltic Sea from all sources of pollution, and thus munitions in the Baltic Sea are addressed by HELCOM since 1993. The convention commits the signatories to take measures to conserve habitats and biological diversity and for the sustainable use of marine resources. In addition, warfare materials potentially constitute a hazard and an obstacle for the utilization of the sea floor for economic purposes. The global ocean economy is predicted to double in size by 2030, as compared to 2010 (OECD 2016). In the Blue Growth Strategy laid out by the European Commission the economic potential for the extended economic usage of the oceans was recognized and focus was placed on five blue growth sectors. Two of these sectors (ocean energy and seabed mining) require the ability to safely access large areas of the sea floor (European Commission 2017). In order to exploit the economic potential of the ocean energy and seabed resources sectors, the detection and removal of warfare materials in

Bacteria are ubiquitous and live in complex microbial communities. Due to differences in physiological properties and niche preferences among community members, microbial communities respond in specific ways to environmental drivers, potentially resulting in distinct microbial fingerprints for a given environmental state. As proof of the principle, our goal was to assess the opportunities and limitations of machine learning to detect microbial fingerprints indicating the presence of the munition compound 2,4,6-trinitrotoluene (TNT) in southwestern Baltic Sea sediments. Over 40 environmental variables including grain size distribution, elemental composition, and concentration of munition compounds (mostly at pmol⋅g –1 levels) from 150 sediments collected at the near-to-shore munition dumpsite Kolberger Heide by the German city of Kiel were combined with 16S rRNA gene amplicon sequencing libraries. Prediction was achieved using Random Forests (RFs); the robustness of predictions was validated using Artificial Neural Networks (ANN). To facilitate machine learning with microbiome data we developed the R package phyloseq2ML. Using the most classification-relevant 25 bacterial genera exclusively, potentially representing a TNT-indicative fingerprint, TNT was predicted correctly with up to 81.5% balanced accuracy. False positive classifications indicated that this approach also has the potential to identify samples where the original TNT contamination was no longer detectable. The fact that TNT presence was not among the main drivers of the microbial community composition demonstrates the sensitivity of the approach. Moreover, environmental variables resulted in poorer prediction rates than using microbial fingerprints. Our results suggest that microbial communities can predict even minor influencing factors in complex environments, demonstrating the potential of this approach for the discovery of contamination events over an integrated period of time. Proven for a distinc