Effects of PET microplastics on the freshwater crustacean 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.

Effect of ABS secondary microplastics on survival, mortality rate, life expectancy and fecundity of the freshwater cladocerans Moina macrocopa

“…Our results indicated that the mortality of cladocerans increased at the minimum concentration of microplastics. This result coincides with that of Castro et al (2023), who reported increased mortality of D. similis when exposed to secondary microplastics and indicate that it could be a consequence of damage to the appendages when they internalized the plastic and, therefore, of decreased feeding. In addition, we found that the microplastics did not stimulate the rst reproductive event since, both in control and in treatments, the rst hatchlings were expelled on the fourth day of age.…”

“…Likewise, on occasions, the microplastics adhered to the carapace and the locomotor antennae, thus limiting the movements of M. macrocopa (Fig. 3b); Castro et al (2023) reported the same situation for the cladoceran Daphnia similis. The adhesion of microplastics to the body of cladocerans may be a frequent event because plastic particles have hydrophobic and electrostatic interactions with organic matter (Galloway et al 2017).…”