POPULATION-DEPENDENT STRESS RESPONSE OF BIVALVE MOLLUSC UNIO TUMIDUS TO IBUPROFEN, MICROPLASTIC AND THEIR MIXTURE
Non-steroidal anti-inflammatory drugs are among the most distributed pharmaceuticals in the surface waters. Microplastics (MPs) in the water column can modulate the effects of drugs, particularly in the filter feeders. This study aimed to indicate the effect of ibuprofen (IBU) and MP on the bivalve molluscs at environmentally relevant sub-chronic exposures utilizing biomarkers of stress and toxicity. The specimens of Unio tumidus from pristine (Pr) and contaminated (Ct) areas were treated with IBU (0.8 µg L−1), MP (1 mg L−1, size 0.1–0.5 mm), or their combination (Mix) for 14 days. Untreated mussels served as controls for pristine and contaminated areas, respectively Pr(C)- and Ct(C)-group. The Pr(C)-group had higher levels of antioxidants Mn-SOD, Cu, Zn-SOD, and catalase as well as lesser levels of oxidative lesions (TBARS and protein carbonyls) and cholinesterase (ChE) than the Ct(C)-group. The only similar response to MP in both populations was the activation of Mn-SOD. Generally, stress responses were dependent on the site rather than on the exposure: Ct-groups showed enhanced stress, whereas Pr-groups were characterized by fairly stable levels of oxidative stress indexes in all the treatments. The action of IBU and Mix increased the ChE activity in both populations and lysosomal integrity in Ct-groups. The integrated biochemical and discriminant analyses indicated the modulation of IBU-induced responses by MP in both populations, particularly in the molluscs from the contaminated area.