Comparative responses and effects of exposure to metallic and nanoparticle zinc in the mussel Mytilus galloprovincialis

Zinc (Zn) nanoparticles (NPs) are widely used in various industrial and commercial applications. Their intensive use in sunscreens, for instance, renders priority to understanding their effects on marine life, to which may be added the intensive use of Zn-based paints and anodes to protect submerged structures. We studied the effects of Zn nanoparticles and ions in the mussel Mytilus galloprovincialis exposed to 1, 10 and 100 μg/L of both zinc forms for up to 28 days. Effects were determined by analysing a battery of biomarkers, from oxidative stress (total antioxidant capacity and catalase activity) to acetylcholinesterase (AChE) activity. The results revealed that mussels responded only marginally differently to ionic and Zn nanoparticles, but also that their response was concentration- and time-dependent, suggesting distinct metabolic modes of action. These variations occurred almost exclusively at the highest concentration tested and were more pronounced as the exposure period increased. An integrated biomarker index (IBR) approach was used encompassing also previous findings (lipid peroxidation and metal accumulation in tissue), which further confirmed that these filter-feeding organisms are considerable targets for zinc exposure in the two forms tested and should be included in studies evaluating the overall toxicological impact of various forms of Zn in the marine environment.