Mapping underwater noise, ships and cetaceans detection with a SeaExplorer glider at a basin level: Feedback from the first 1000km-long acoustics exploration of the Western French Mediterranean Sea

In response to concerns about the impact of manmade noise on marine ecosystems, research and regulatory communities are currently collecting in situ measurements of oceanic noise levels. The objectives of in situ measurements are threefold. First, they provide necessary inputs, i.e. the acoustic signatures of individual ships to feed the models. Second, they are used to calibrate models for mapping of shipping noise. Third, they are processed to assess marine biodiversity through the sounds emitted by marine animals (cetaceans, fishes, invertebrates). The usefulness of the data collected depends on the duration of acquisition and measurement diversity (e.g., shipping density, water depth). Gliders are ideal candidates to collect noise level data across oceanic basins and over long time periods. Here we show results from a SeaExplorer glider equipped with a high quality acoustics payload travelling for 30 days (09/15/2017-10/15/2017) along a 1000km-long transect of the Western French Mediterranean Sea. The trajectory of the glider was chosen to sample the highest and lowest shipping densities. We here report on the statistical distribution of oceanic noise levels in the bandwidths assessed by the European Marine Framework Strategy Directive, the detection of cetaceans and ships sounds along this transect.