Integrated biomarker assessment of the effects exerted by treated produced water from an onshore natural gas processing plant in the North Sea on the mussel Mytilus edulis

► Significant biomarker responses in mussels exposed to 0.01-0.5% PW. ► Integrated biomarker responses showed a clear biological effect at 0.01-0.5% PW. ► The highest PW concentration had a lower biomarker response than expected. ► Benefits of an integrated biomarker approach in environmental monitoring.