Underwater operational noise level emitted by a tidal current turbine and its potential impact on marine fauna

Marine renewable energy development raised concerns over the impact of underwater noise. We assessed the acoustic impacts of an operating tidal current turbine (Paimpol-Bréhat site, France) on marine fauna. The turbine’s source level (SL) was estimated using 19 acoustic drifting transects at distances between 100m to 2400m from the device. SL ranges from 118 to 152dBre1μPa@1m in the third-octave bands at frequencies between 40 and 8192Hz, a noise level comparable to the one emitted by a 19m boat travelling at 10kt. The SL was used to estimate the impact of the turbine’s noise based on acoustic propagation simulations. The overall acoustic footprint of the device corresponds to a disk of 350 meters radius. Our results showed that within this footprint, physiological trauma is improbable but behavioral disturbance may occur up to 350m around the device for marine mammals (impact limited by the footprint area), and 55m, 5m and 5m respectively for pollocks, sea basses and a shrimp species. Feedbacks from this study show that the assessment of TTS and PTS risk areas for marine mammals is rather mature, but there are still many uncertainties about the assessment of risk areas for behavioral disturbance and masking for fishes and marine invertebrates.