Polystyrene microplastics do not affect juvenile brown trout (Salmo trutta f. fario) or modulate effects of the pesticide methiocarb

Abstract

Background: There has been a rising interest within the scientific community and the public about the environmental risk related to the abundance of microplastics in aquatic environments. Up to now, however, scientific knowledge in this context has been scarce and insufficient for a reliable risk assessment. To remedy this scarcity of data, we investigated possible adverse effects of polystyrene particles (10 4 particles/L) and the pesticide methiocarb (1 mg/L) in juvenile brown trout (Salmo trutta f. fario) both by themselves as well as in combination after a 96 h laboratory exposure. PS beads (density 1.05 g/mL) were cryogenically milled and fractionated resulting in irregular-shaped particles (< 50 µm). Besides body weight of the animals, biomarkers for proteotoxicity (stress protein family Hsp70), oxidative stress (superoxide dismutase, lipid peroxidation), and neurotoxicity (acetylcholinesterase, carboxylesterases) were analyzed. As an indicator of overall health, histopathological effects were studied in liver and gills of exposed fish. Results: Polystyrene particles by themselves did not influence any of the investigated biomarkers. In contrast, the exposure to methiocarb led to a significant reduction of the activity of acetylcholinesterase and the two carboxylesterases. Moreover, the tissue integrity of liver and gills was impaired by the pesticide. Body weight, the oxidative stress and the stress protein levels were not influenced by methiocarb. Effects caused by co-exposure of polystyrene microplastics and methiocarb were the same as those caused by methiocarb alone. Conclusions: Overall, methiocarb led to negative effects in juvenile brown trout. In contrast, polystyrene microplastics in the tested concentration did not affect the health of juvenile brown trout and did not modulate the toxicity of methiocarb in this fish species.

Interacting Effects of Polystyrene Microplastics and the Antidepressant Amitriptyline on Early Life Stages of Brown Trout (Salmo trutta f. fario)

“…PS MP did neither affect the AChE activity nor the activity of two CbEs of brown trout. Similar results were found for juvenile brown trout exposed to the same PS MP (10 4 particles/L) for 96 h [86]. Furthermore, PS MP (45 µm) did not cause alterations in the activity of AChE in zebrafish [29].…”

“…Nevertheless, the data basis of the chemical analytic seems to be too limited to draw clear conclusions about the sorption of amitriptyline to MP. Only few studies found, like the present study, no interaction between MP and pollutants [86,90]. However, it cannot be excluded that this might have been resulting from a bias against the publication of negative results [27].…”

“…Also, Chen, et al [29] did not observe any influence of PS MP on the activity of catalase (CAT) and glutathione peroxidase (GPx) but they reported a significant decrease in the level of the reduced form of glutathione (GSH) in zebrafish larvae. In juvenile brown trout, also no effect of PS MP on oxidative stress was found [86]. Furthermore, in common gobies (Pomatoschistus microps) the LPO level was not affected by PE MP exposure in several studies [33,[87][88][89].…”

Microplastic Contamination in Freshwater Environments: A Review, Focusing on Interactions with Sediments and Benthic Organisms

“…Nonetheless, the role of MPs as vectors of contaminants still presents contradictory interpretations [124,125]: while some ecotoxicological studies have determined that plastic can have a synergic effect with respect to pollutants (e.g., [120,126,127]), other studies have reported negligible changes in contaminant uptake in the presence of MPs (e.g., [128][129][130]).…”

Microplastics and the functional traits of fishes: A global meta‐analysis

“…Yin et al (2019) found that microplastic exposure altered behavioural traits, energy reserves and the nutritional quality of demersal black rockfish. However, some studies have concluded that microplastics have no effect on organisms, unless associated with organic contaminants (Le Bihanic et al, 2020; Schmieg et al, 2020).…”