Metabolomic responses in freshwater benthic invertebrate, Chironomus tepperi, exposed to polyethylene microplastics: A two-generational investigation
Hsuan-Cheng Lu, Anupama Kumar, Steven D. Melvin, Shima Ziajahromi, Peta A. Neale, Frédéric D.L. Leusch
Abstract
The accumulation of microplastics (MPs) in sediments could pose risks to benthic organisms and their progeny. Here, we examined effects on traditional apical endpoint along with changes to whole body metabolite profiles induced by irregular shaped polyethylene MPs (1-45 µm) at environmentally relevant concentrations (125, 250, 500 and 1000 MPs/kg sediment) in Chironomus tepperi using a two-generation exposure regime. Survival and emergence of C. tepperi were negatively affected in the parental generation at the two highest concentrations, whereas endpoints associated with growth were only impacted at 1000 MPs/kg sediment. Metabolites associated with several amino acid and energy metabolism pathways were present at lower abundances at the highest exposure concentration suggesting an overall impact on bioenergetics which relates to the inhibition of food acquisition or nutrient assimilation caused by ingestion of MPs, rather than a traditional receptor-mediated toxicity response. In contrast, no significant effects on apical endpoints were observed in the continuous exposure of first filial generation, and lactic acid was the only metabolite that differed significantly between groups. Larvae in unexposed conditions showed no differences in survival or metabolite profiles suggesting that effects in the parental generation do not carry over to the next filial generation. The findings provide evidence on the underlying impacts of MP ingestion and potential adaption to MP exposure of C. tepperi. As contaminants of emerging concern, microplastics have been widely reported in global freshwater environments and freshwater sediment is considered as a major sink. Despite ingestion of microplastics is well documented in aquatic organisms, there is limited information on effects of microplastics on the freshwater benthic invertebrates, especially at realistic environmental concentrations and across generations. This study provides insight into the lethal effects of microplastics on C. tepperi over two generations. Additionally, this study provides the first evaluation of metabolomics profiling to unravel the potential organismal and physiological responses of microplastics ingestion in C. tepperi.