Spatial impact of wind farm construction on harbour porpoise detectability

To combat impacts of climate change, offshore wind farm construction is accelerating globally. Accompanying increases in construction activity have raised concerns about associated noise impacts on acoustically sensitive species, including harbour porpoises (Phocoena phocoena). This study investigated spatial impacts from the construction of ScottishPower Renewables’ East Anglia ONE (EA1) offshore wind farm (310 pin-piles), located off southeast England, on porpoises belonging to the North Sea Management Unit. Data on porpoise presence and received noise levels were collected from up to 12 monitoring stations around EA1 before, during, and after construction from March 2018 to June 2019, using automated click detectors (C-PODs) and full bandwidth acoustic recorders. Acoustic recordings were used to calibrate a sound propagation model to assess porpoise responses to received noise levels. Analysis of porpoise detection data in the presence and absence of pin-piling revealed negative effects of piling, with an overall decrease in porpoise detection probability out to 14.0 km from piling activity. The predicted frequency-weighted received level at this distance was 103.0 dB re 1 μPa2s SEL. These observations inform our current knowledge of pin-piling-related impacts on harbour porpoises at the spatial scale of the individual wind farm, which is crucial to develop effective mitigation strategies