Trends in bioaccumulation and metabolite profiles in Mediterranean mussels with sub lethal exposure to mixtures of trace metals

Trace metals are major environmental contaminants, and the accumulation of trace metals could cause changes to the metabolism of marine organisms. In order to understand trends in bioaccumulation and changes in metabolic pathways in marine mussels during short-term and long-term exposure to trace metal mixtures, wild Mediterranean mussels (Mytilus galloprovincialis) were exposed to natural seawater spiked with two sub lethal concentrations of a mixture of copper (Cu), zinc (Zn), and lead (Pb) for 30 days. Mussels were collected every 5 days and trace metal levels in the whole bodies were measured. The gills of mussels collected on day 5 and day 30 were sampled separately. Trace metal levels in whole bodies of these samples were measured and metabolites in the gill tissue extracted, profiled, identified, and compared between groups with different exposure time and trace metal levels. The results showed continuous increase in body burdens of Cu and Pb in mussels throughout the exposure period, while Zn accumulation reached a plateau after day 10 in the whole body and gills. The metabolomics analysis demonstrated that multiple metabolites were down-regulated and multiple metabolic pathways possibly interrupted by exposure to the mixture of trace metals. This study provides extensive knowledge that the effects of Cu, Zn, and Pb exposure on the metabolic pathways have the potential to result in reduced fitness of Mediterranean mussels and demonstrates potential of GC-MS based untargeted metabolomics to be used as a part of trace metal pollution evaluation and ecosystem health monitoring.