Anthropogenic particles and legacy pollutants combined with transcriptomic and multi-biomarker responses for an integrated assessment of the health status of mussels Mytilus galloprovincialis in two locations of the Bay of Biscay

Integrated monitoring approaches combining measurement of pollutants and biomarker responses are widely used to study health status of marine ecosystems in the Bay of Biscay (BoB). The aim of this study was to assess the health status of mussels Mytilus galloprovincialis from the estuary of Plentzia and the marina of Arriluze in the BoB, focusing on anthropogenic particles (APs), trace metals, PAHs and PCBs and applying a multi-biomarker approach. Higher levels of APs, including microplastics (MPs), were recorded in Plentzia, establishing baseline data for future MP monitoring. A declining trend in PAHs and PCBs in mussels at the study sites agrees with the lack of differences in peroxisomal acyl-CoA oxidase activity. The content of all metals in sediments and of Cd and Pb in mussels was higher in Arriluze. Also levels of DNA strand breaks were higher in Arriluze. An altered sex ratio in Arriluze and vcl transcription levels in Plentzia suggest endocrine disruption effects. Volume density of basophilic cells and prevalence of histopathologies was higher in Arriluze whereas the prevalence of Nematopsis sp. was prominent in Plentzia, highlighting potential interactions between pollutants and pathogens. The condition index was higher in Arriluze, possibly because of its higher organic matter content. Overall, the Integrative Biomarker Response (IBR) index revealed higher stress levels in Arriluze compared to Plentzia. These results are relevant to understand the long-term trends of emerging and legacy pollutants and the health status of sentinel mussels in the BoB, where different pressures and stress sources might act in combination.