Ecophysiological responses of juvenile great scallops (Pecten maximus) exposed to pile driving sound playback

The global expansion of offshore wind energy as a climate mitigation strategy is increasing anthropogenic sound in coastal marine environments. Pile driving during construction produces intense impulsive sound that propagates over kilometers underwater, yet its ecophysiological consequences for locally abundant benthic invertebrates remain poorly understood. We investigated behavioural and metabolic responses of juvenile Pecten maximus to pile driving sound playback under controlled laboratory conditions simulating received levels expected approximately at 2-20 km from an offshore wind farm construction site, depending on pile diameter. An integrated framework combining continuous valve activity monitoring with repeated measurements of metabolic rates was implemented in a before-during-after exposure design. No clear behavioural or metabolic responses were detected under the simulated exposure conditions reproduced in this study. Although metabolic rates varied across experimental sequences, these changes were independent of acoustic treatment, suggesting intrinsic temporal or feeding-related dynamics. Indeed, oxygen consumption was strongly and positively associated with spontaneous swimming activity, reflecting the energetic cost of phasic adductor muscle contractions and subsequent oxygen debt repayment. These findings indicate that pile driving sound playback at kilometer-scale exposure may not induce detectable short-term energetic disruption in juvenile P. maximus. Effects at closer range, under higher intensities, or during prolonged exposure warrant further investigation to better assess ecological risk in scallop-dominated ecosystems.