Conference_programme: 27.1 - Underwater Noise I: Monitoring and modelling of the Ambient Noise

Lecture: Three-dimensional soundscape of a tidal site (Raz Blanchard, France): benthic biophony & bed load transport geophony

Author(s): Lossent Julie, Gervaise Cédric, Di Iorio Lucia, Bourdon Raphael, Clec'H Didier, Lejart Morgane

Summary:
Marine renewable energy development raised concerns over their potential impact. However, environments on tidal sites are very complicated to monitor because of the high current speed, especially regarding benthic populations’, fishes’, marine mammal’s behavior, sediment movements or non-destructive testing on the tidal turbine device. Passive acoustic monitoring could address these challenges. Benthic invertebrates emit high energetic broadband transient sounds (BTS) with peak frequencies ranging from 1.5 to 60kHz. Bed load transport emits also BTS whose peak frequencies and Sound Pressure Levels are respectively linked to the bedload grain size and current speed. By the very nature of these sounds constituting a part of the tidal site soundscape, these pulses are well adapted to the detection and the measurement of their Time Difference Of Arrival (TDOA) to the hydrophones of the array, input data necessary for localization. We deployed a 7T pyramidal structure (3.6m*3.6m*4m) with 4 hydrophones on a future tidal current turbine site (Raz Blanchard – Normandie Hydro, France) for two months in October 2017. Thank to this recording array we detected and localized benthic and bedload transport BTS to build maps of the impulsive soundscape of the site in two or three dimensions ({azimuth, elevation} or {x, y, z}). In the context of marine renewable energy impact assessment, this method allows: to monitor and map simultaneously in 3D 1) the soniferous benthic invertebrates to estimate the acoustic dynamic of the site, 2) the bed load transport to evaluate the grain size and 3) the marine mammals’ behavior in vicinity of the turbine to deal with the behavioral impact and to study 4) the soniferous fishes’ communications and 5) the noise emitted by the operating marine current turbine to conduct non-destructive testing for the companies involved.

Corresponding author

Name: Ms Julie Lossent

e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Country: France