Stage-specific metabolic responses in blue mussels to marine shipping-related acoustic and chemical stressors

Maritime traffic exposes coastal organisms to both acoustic disturbance and chemical pollution, yet how these stressors affect and interact across early developmental stages remains poorly understood. We investigated stage-specific metabolic responses of blue mussel (Mytilus edulis) larvae to shipping-related noise, chemical pollution, and their combination using untargeted nuclear magnetic resonance-based metabolomics. Metabolic profiles were analysed in D-larvae and post-larvae exposed to noise or chemical pollution, as well as in post-larvae originating from chemically exposed embryos and subsequently subjected to acoustic stress during metamorphosis. During embryogenesis, acoustic and chemical stressors elicited largely overlapping metabolic responses, primarily involving modulation of free amino acid pools and nitrogen-related pathways. In contrast, post-larvae exhibited distinct, stressor-specific metabolic signatures. Acoustic exposure was associated with increased metabolic turnover and mobilisation of energetic substrates, whereas embryonic chemical exposure resulted in persistent metabolic constraints during metamorphosis, reflected in energy balance and membrane-associated metabolites. In post-larvae originating from chemically exposed embryos and subsequently exposed to shipping noise during metamorphosis, metabolic profiles closely resembled those induced by chemical stress alone, indicating persistent carry-over effects of embryonic chemical exposure. Together, these results demonstrate that developmental stage strongly modulates metabolic sensitivity to shipping-related stressors and that early-life chemical exposure can shape metabolic plasticity at later life stages.