Effects of chemical leachates from offshore wind farm infrastructure on heart rate and valve gape of blue mussels

Offshore wind farms (OWFs) play a key role in combating climate change, but the coatings used to protect submerged infrastructure can leach potentially harmful chemicals into the marine environment. These leachates may affect marine species colonizing OWF structures or being cultured near OWFs, such as blue mussels. To assess the impacts, we monitored valve gape behaviour and heart rate in Mytilus edulis exposed to coating leachates under controlled conditions, followed by a thermal ramping to assess potential constraints in their stress performance. Using non-targeted screening with two-dimensional gas chromatography and high-resolution mass spectrometry, we identified nine chemicals in the leachates plausibly assigned to the coatings, including alcohols, ketones, lactones, bromobenzenes, dibromophenols, and polycyclic aromatic hydrocarbons. At constant temperatures, exposed mussels showed both up to 12 % reduced and up to 18 % increased daily cardiac arrest compared to control mussels. However, during cardiac activity heart rate and valve gape were similar among treatments. Leachate exposure did not lead to reductions in fitness endpoints during the thermal ramping, i.e. the temperature at which heart rate was maximal (21.3 ± 0.4 °C) and valves started to close (19.2 ± 0.6 °C). Non-targeted screening does not allow for comparisons of chemical concentrations from field samples, yet the painted surface to volume of seawater ratio used here potentially led to much higher leachate concentrations than any environmentally relevant conditions. Future research on leachates from other OWF sources, such as sacrificial anodes, is needed to gain a comprehensive understanding of ecological risks and support sustainable OWF development.