Life stage-specific effects of tire particle leachates on the cosmopolitan planktonic copepod Acartia tonsa

Abstract

Tire wear particles (TWP) are a major source of microplastics in the aquatic environment and the ecological impacts of their leachates are of major environmental concern. Among marine biota, copepods are the most abundant animals in the ocean and a main link between primary producers and higher trophic levels in the marine food webs. In this study, we determined the acute lethal and sublethal effects of tire particle leachates on different life stages of the cosmopolitan planktonic copepod Acartia tonsa. Median lethal concentration (LC₅₀, 48 h) ranged from 0.4 to 0.6 g L^-1 depending on the life stages, being nauplii and copepodites more sensitive to tire particle leachates than adults. The median effective concentration (EC₅₀, 48 h) for hatching was higher than 1 g L^-1, indicating a relatively low sensitivity of hatching to tire particle leachates. However, metamorphosis (from nauplius VI to copepodite I) was notably reduced by tire particle leachates with an EC₅₀ (48 h) of 0.23 g L^-1 and the absence of metamorphosis at 1 g L^-1, suggesting a strong developmental delay or endocrine disruption. Leachates also caused a significant decrease (10-22%) in the body length of nauplii and copepodites after exposure to TWP leachates (0.25 and 0.5 g L^-1). We tested a battery of enzymatic biomarkers in A. tonsa adult stages, but a sublethal concentration of 50 mg L^-1 of tire particle leachates did not cause a statistically significant effect on the measured enzymatic activities. Our results show that tire particle leachates can negatively impact the development, metamorphosis, and survival of planktonic copepods. More field data on concentrations of TWPs and the fate and persistence of their leached additives is needed for a better assessment of the risk of tire particle pollution on marine food webs.

Keywords: Copepods; Development; Leachates; Life cycle; Tire wear particles; Toxicity.