Offshore exposure experiments on cuttlefish indicate received sound pressure and particle motion levels associated with acoustic trauma

Marta Solé,Michel André,Peter Sigray,Emilia Lalander,Marc Lenoir,Mike Van Der Schaar

doi:10.1038/srep45899

Abstract

Recent findings on cephalopods in laboratory conditions showed that exposure to artificial noise had a direct consequence on the statocyst, sensory organs, which are responsible for their equilibrium and movements in the water column. The question remained about the contribution of the consequent near-field particle motion influence from the tank walls, to the triggering of the trauma. Offshore noise controlled exposure experiments (CEE) on common cuttlefish (Sepia officinalis), were conducted at three different depths and distances from the source and particle motion and sound pressure measurements were performed at each location. Scanning electron microscopy (SEM) revealed injuries in statocysts, which severity was quantified and found to be proportional to the distance to the transducer. These findings are the first evidence of cephalopods sensitivity to anthropogenic noise sources in their natural habitat. From the measured received power spectrum of the sweep, it was possible to determine that the animals were exposed at levels ranging from 139 to 142 dB re 1 μPa2 and from 139 to 141 dB re 1 μPa2, at 1/3 octave bands centred at 315 Hz and 400 Hz, respectively. These results could therefore be considered a coherent threshold estimation of noise levels that can trigger acoustic trauma in cephalopods.

Highlights

Recent findings on cephalopods in laboratory conditions showed that exposure to artificial noise had a direct consequence on the statocyst, sensory organs, which are responsible for their equilibrium and movements in the water column
In previous studies on four species of cephalopods, the common Mediterranean cuttlefish (S. officinalis), common octopus (Octopus vulgaris), the European squid (Loligo vulgaris) and the southern shortfin squid (Illex coindetii)[18,19,20], we showed that exposure to artificial noise had a direct consequence on the functionality and physiology of the statocysts, sensory organs, which are responsible for invertebrate equilibrium and movements in the water column
As previously described in details in André et al.[37], it was suggested that particle motion could encompass the whole body of cephalopods and cause it to move with the same phase and amplitude: the statolith organs would be stimulated by whole-body displacements and would act as a harmonic oscillator[29,30,31,32,33,34,35]

Summary

Introduction

Recent findings on cephalopods in laboratory conditions showed that exposure to artificial noise had a direct consequence on the statocyst, sensory organs, which are responsible for their equilibrium and movements in the water column. The possibility to measure whole body (distance, velocity and acceleration) vibration, as a direct stimulus eliciting statocyst response, and offered the scientific community a new level of understanding of the marine invertebrate sensitivity to sound[37] These techniques were already applied to other species such as amphibians, reptiles and crustaceans to measure specific organ vibration[38,39,40], this constituted the first measurement of the whole body vibration induced by underwater sound that had been performed in any marine organism. Offshore noise controlled exposure experiments (CEE) on common cuttlefish (Sepia officinalis), were conducted at three different depths and distance from the source to measure the response of exposed animals to different sound pressure and particle motion levels and quantify the response of the statocyst sensory epithelia

Methods

Results

Conclusion