Response and recovery of Baltic Sea blue mussels from exposure to pharmaceuticals

Abstract

Physiological responses to, and recovery from, exposure to 3 concentrations of a pharmaceutical mixture (diclofenac and propranolol) were examined experimentally in Baltic Sea blue mussels Mytilus edulis trossulus collected with increasing distance to a wastewater treatment plant (WTP) outlet. Respiration, absorption efficiency and consumption were measured, and also combined into scope for growth (SFG). The response and recovery patterns varied both between exposure concentrations and sampling site within the bay. After exposure, mussels exposed to the highest concentration (2000 μg l-1) in general had lower SFG, and mussels from 2 (out of 3) sites exposed to the medium concentration (200 μg l-1) had higher SFG than the controls. In general, mussels from the 2 sites nearest the WTP recovered from the exposure response, while individuals collected further from the WTP outlet were more affected by the exposure and did not recover to the same extent. The response pattern of consumption was mainly affected by exposure concentration, whereas respiration was affected by all 3 factors (concentration, time of measurement, sampling site). Absorption efficiency was not affected at all. The differences in responses and recovery patterns could possibly be explained by the mussels sampled closer to the WTP having a history of higher food availability, improving their general health status, and/or a history of pre-exposure to natural disturbances, as well as to the test substances, via the WTP effluent. Pre-exposure to stressors could have both positive and negative impact on a community by increasing the resilience towards some stressors, but may also reduce the adaptability when facing other stressors.