Microplastic vector effects: are fish at risk when exposed via the trophic chain?

, Agathe Bour, Sturve Joachim, Höjesjö Johan, Carney Almroth Bethanie.

Trophic transfer has been identified as an important exposure route to microplastics (MPs) in predator species. Many chemicals are sorbed on MPs and can potentially be transferred to organisms in contact with MPs, including via the trophic route (“vector effect” of MPs). However, there is currently no consensus on whether MPs represent a significant exposure pathway to chemicals in contaminated habitats, where other contamination pathways could be predominant. Despite their relevance, effect studies, including vector effect studies, on fish exposed to MPs via trophic chains are currently very scarce. To fill that gap, we exposed three-spined stickleback (Gasterosteus aculeatus) to MPs via prey ingestion, in a long-term experiment. MPs were either pristine or spiked with chlorpyrifos (CPF), an organophosphate pesticide. To understand the specific role of MPs as a vector of contamination, a condition were preys were directly contaminated with CPF in solution was also included. CPF accumulation was observed in fish exposed to CPF-spiked MPs (MP-CPF), confirming the vector potential of MPs. However, CPF accumulation was more important in fish exposed to CPF via prey. Interestingly, CPF organ distribution differed between groups, suggesting that chemical exposure via MPs could alter organ distribution of chemicals. This can result in a change in the organs most at risk, likely increasing intestine exposure. We also assessed the effects of such exposure on fish, including neurotoxicity (AChE inhibition) and organism performance (feeding, locomotion and environment exploration behavior). Different patterns were observed depending on the exposure conditions. Especially, we observed significant AChE inhibition and hyperactivity in fish exposed to MP-CPF, which could result in increased vulnerability to predation.

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