Abstract:

Microplastics (MPs) pollution has become one of the most pressing environmental issues to date. In freshwater systems, high levels of MPs, especially in riverine sediments, have been reported. Concerningly, the effects of MPs to freshwater macroinvertebrates, a key component of freshwater food webs, remains unclear. This study aimed to determine the risk of MPs to freshwater macroinvertebrates through toxicity assessments using ecologically realistic exposures. We used sludge worms (Tubifex tubifex), and file ramshorn snails (Planorbella pilsbryi), and three types of MPs, polystyrene microbeads (6 and 45 µm) and polyester microfibers (100 µm). For each species, toxicity and accumulation were assessed following exposure to each MPs type. Biofouled MPs were also included to replicate the microbial attachment and biofilm formation typically found on MPs in natural systems. To assess toxicity, reproduction and survival were measured across all tests. MPs accumulation was also assessed following each exposure, with a gut clearance period to determine MPs excretion efficiency. Additionally, the host microbiomes were examined to determine the potential for dysbiosis following MPs exposure. To date, no significant effects to reproduction or mortality have been observed for any species, across any MPs type or condition. Host microbiome analysis is currently underway. In P. pilsbryi, significant accumulation of MPs was reported, but it varied according to MPs type, size, and condition. No significant MPs accumulation occurred in T. tubifex. However, P. pilsbryi were able to efficiently excrete ingested MPs. Overall, results will help understand the potential impacts of MPs to freshwater macroinvertebrates and the risks of MPs contamination in freshwater ecosystems.