Impacts of pile-driving noise on neurotransmitter- and immune-parameters of the thick-shell mussel (Mytilus coruscus)

Anthropogenic underwater noise, an emerging source of pollution, has aroused great public concern over its potential adverse impacts on aquatic organisms. Although bivalve mollusks may be sensitive to noise pollution, impacts of anthropogenic underwater noise on this group of species are far from being fully understood. In this study, the survival rate upon pathogenic microbial (Vibrio parahaemolyticus) challenge as well as cellular and humoral immune-related parameters upon 4-week pile-driving noise exposure at 80 and 90 dB re 1 μPa were assessed in the thick-shell mussel (Mytilus coruscus). Additionally, the impacts of pile-driving noise exposure on in vivo levels of key immune-related neurotransmitters and expression of neurotransmitter- and immune-related target genes were screened. Furthermore, using data obtained from the same individual sample, the potential association of humoral immune parameters with those of neurotransmitters was evaluated statistically. Our results demonstrated that exposure to pile-driving noise significantly boosted mussel mortality in the pathogenic bacterial challenge assay and markedly impaired both cellular and humoral immunity. Noise exposure also interfered with the expression of genes encoding neurotransmitter-metabolic enzymes and core immune-regulatory neurotransmitters (GABA, DA, ACh, and 5-HT), resulting in a disruption of neurotransmitter homeostasis. Moreover, correlation analysis revealed strong correlations of humoral immune parameters with neurotransmitter ones. Collectively, our data suggest that disrupting neurotransmitter homeostasis and thereby interfering with NEI immune regulation might be a potential route through which pile-driving noise exposure undermined immunity of the thick-shell mussel, the far-reaching impacts of which warrant close attention.