Line Hermannsen

LineAnthropogenic underwater noise pollution is rapidly increasing in marine environments worldwide. This is a result of the continuous increase in human activities at sea including international shipping, oil and gas explorations with seismic airguns and pile-driving during developments of offshore wind farms, but also the rapid increase in recreational activities in many coastal environments, including high-speed motor boating and jet skiing. Since marine anthropogenic activities often overlap with important habitats of marine mammals that rely on sound to perform vital functions (e.g. finding and acquiring food, communicating and navigating), the fitness of these species is at risk of being compromised with increased underwater noise levels.

I work with characterising underwater noise emissions from various anthropogenic marine activities and investigating how anthropogenic noise affects marine mammals, with the aim to reach good mitigation measures for sustainable management of the marine environment. More specifically, my work has included: 1) showing that the two low-frequency bands of the European Marine Strategy Framework Directive (63 and 125 Hz) are insufficient to assess noise impacts on harbor porpoises (Phocoena phocoena) in shallow water habitats, as various ships also emit noise at mid-to-high frequencies within porpoise hearing (Hermannsen et al. 2014), 2) showing that seismic airguns have a low-frequency emphasis, but also emit considerable noise at higher frequencies within porpoise hearing and thereby may cause significant behavioral responses out to several kilometres, well beyond the commonly used shut-down zone of 500 metres around seismic surveys (Hermannsen et al. 2015), and 3) showing that a “seal scarer”, used as an acoustic mitigation device for marine species prior to offshore pile driving, is effective in scaring harbor porpoises away, whereas seals react very differently and may even approach a seal scarer device, highlighting that further developments are necessary to ensure a balanced mitigation of different species in multi-species habitats (Mikkelsen et al. 2017). My current projects focus on characterising the noise contribution of ships and recreational boats in different coastal environments.

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