Assessing the impacts of anthropogenic sounds on early stages of benthic invertebrates: The 'Larvosonic system'.

Noise produced by human activities has increased in the oceans over the last decades. Whereas most studies have focused on the impact of anthropogenic noise on marine mammals and fishes, those focusing on marine invertebrates  are  rarer  and  more  recent,  especially  when  considering  peri-metamorphic  benthic  stages,  highly sensitive to  anthropogenic perturbations. A  careful review  of the literature reveals  a  simplistic characterization of the acoustics within the containers used to quantify larval and juvenile responses to noise, thus weakening the conclusions of such works. To address this problem, we developed the Larvosonic system, a laboratory tank equipped  with  acoustic assets  to  assess  the  impacts  of  noise  on  young  stages  of  marine  invertebrates.  We  first provide  a  careful  analysis  of  the  tank  sound  field  using  different  sound types,  and  we  assess  the  effects  of expanded polystyrene units on the sounds emitted by a professional audio system in order to dampen reverbera- tion  and  resonance. Then,  we  apply  this  acoustic  calibration  to  the  effects  of  both  pile  driving  and  drilling noises on postlarvae of the scallop bivalve Pecten maximus. Acoustic recordings highlight that diffuser and bass trap  components  constitute  effective  underwater  sound  absorbents,  reducing  the  reflection  of  the  whole  fre- quency bandwidth. Scallop experiments reveal that both type and level of the tested noise influenced postlarval growth,  with  interactive  effects  between  trophic  environment  and  noise  level/spectra. The  Larvosonic  system thus constitutes an efficient tool for bioacoustics research on bentho-planktonic invertebrate species."