A Case Study-Based Analysis of Uncertainties on the Assessment of Impulsive Underwater Noise for the Marine Strategy Framework Directive

The Marine Strategy Framework Directive (MSFD) has been an important driver for progress in monitoring and assessment of impulsive underwater noise in the marine environment of the European Union. An important achievement of the MSFD implementation was the development of regional noise registries, providing the data basis for assessments. Recently, the EU has made tremendous efforts to propose harmonized assessment approaches and first-of-their-kind regional quantitative thresholds for impulsive underwater noise. In light of these newly developed thresholds values, we analyze the suitability of the available data in the noise registries for assessment purposes under the MSFD and review sources of uncertainties regarding quantitative results. We present three regional case studies located in the North Sea, the Baltic Sea and the Mediterranean Sea. For each of these regions, a sound-intensive activity was selected that aligned with a realistic impulsive noise event reported for the region. We made use of available data in the noise registries and applied the EU Guidance recommended for the description of impulsive noise sources, but also used alternative approaches and observations as comparison. The case study analysis includes the evaluation of data availability, data quality and data accuracy in the noise registries, and identifies corresponding consequences of the data for the uncertainty and interpretability of assessment results, especially for the quantitative evaluation of habitat areas impacted by noise. Finally, we make suggestions for the improvement of the data basis in the noise registries and the optimization of the assessment accuracy.

Automated summary

The Marine Strategy Framework Directive (MSFD) has played a significant role in advancing the monitoring and assessment of impulsive underwater noise in the European Union's marine environment. One important outcome of MSFD implementation is the development of regional noise registries that provide crucial data for assessments. Recent efforts by the EU have resulted in the proposal of harmonized assessment approaches and regional thresholds for impulsive underwater noise. This study analyzes the suitability of the data in the noise registries for MSFD assessments, examines sources of uncertainty in quantitative results, and presents regional case studies to evaluate data availability, quality, accuracy, and their impact on the interpretation of noise impact on habitat areas.