Effects of PET microplastics on the freshwater crustacean Daphnia similis Claus, 1976

Efeitos dos microplásticos de PET no crustáceo de água doce Daphnia similis Claus, 1976

Abstract:

Aim

In this study, we investigated the effects of secondary PET microplastics (< 53 µm) on the Daphnia similis basic life-history parameters survival, age at first reproduction and total offspring number. We also analyzed D. similis enzymatic activity (superoxide dismutase, catalase and glutathione-S-transferase) at sub-effect concentrations.

Methods

We performed acute and chronic toxicity tests using six PET microplastics concentrations (0, 10², 10³, 10⁴, 10⁵ and 10⁶ part. mL^-1). We also applied an exposure test to analyze superoxide dismutase, catalase and glutathione-S-transferase activities at sub-effect concentrations.

Results

D. similis mortality increased (LC₅₀ = 1 x 10⁵ part. mL^-1), reproduction decreased (EC₅₀ = 10⁵ part. mL^-1) and time to first offspring was delayed by 5 days at the highest microplastic concentration after 21 days exposure. Neither mortality nor alterations in superoxide dismutase, catalase or glutathione-S-transferase activities were detected after 48 h exposure. Microplastics adhered to D. similis body appendages, causing altered swimming behavior.

Conclusions

Lack of acute toxicity but occurrence of chronic effects serve as a warning for caution when concluding about microplastics non-toxicity in short-term tests. Microplastics had unexpected effects with important ecological implications. Our results contribute to fill the knowledge gaps on the effects of microplastic pollution on aquatic ecosystems, especially under long-term exposure.

Keywords:
plastic; toxicity; polyethylene terephthalate; zooplankton