Impulsive pile driving sound does not induce hearing loss in the longfin squid (<i>Doryteuthis pealeii</i>)

Offshore windfarms are a key means to produce clean energy as we seek to limit climate change effects. Impulsive pile driving used for their construction in shallow water environments is among the most intense anthropogenic sound sources. There is an increasing understanding that an array of marine invertebrates detects acoustic cues, yet little is known about how pile driving sound could impact their sound detection abilities. We experimentally quantified potential changes in sound sensitivity for an abundant, commercially and ecologically important squid species (Doryteuthis pealeii) exposed to actual in situ pile driving. The pile was 0.3-m diameter and 10-m long; hammer energy reached 16 kJ per strike. Sound detection thresholds were determined using auditory evoked potentials in animals with no exposure, after one 15-min or five repeated 15-min long pile driving sound sequences, corresponding to cumulative sound exposure levels of 110 and 131 dB re (1 μm s-2)2 s for acceleration and 187 and 214 dB re (1 μPa)2 s for pressure. We found no statistical evidence of temporary threshold shifts in any squid exposed to pile driving sound sequences. These results, combined with companion behavioral studies, suggest that squid may be robust to the sound impacts during offshore windfarm construction.