Environmental impact assessment of continuous underwater noise in the Baltic Sea

Here we present the first basin scale implementation of the new EU Technical Group on Underwater Noise framework for assessing the environmental status of low frequency continuous noise. The purpose of the study was to demonstrate the efficiency of the framework for assessment of the effects of low frequency continuous noise on marine life in the Baltic Sea and its subbasins. 2018 was chosen as the assessment period because it was a year with good coverage of monitoring data. The assessment was based on modeled levels in two 125 and 500 Hz decidecade bands deemed relevant for the indicator fish and marine mammals respectively. The risk for disturbance and the risk for masking were assessed in parallel. It was assessed that the low frequency continuous noise is probably having a negative impact on indicator fish species. Simultaneously, it did not have a significant negative impact on marine mammals. We also discuss the factors that affect the reliability of these results and give our opinions on the steps forward in order to improve the reliability in the future.