Microplastics decrease the toxicity of triphenyl phosphate (TPhP) in the marine medaka (Oryzias melastigma) larvae

• Published in: The Science of the total environment Vol. 763; p. 143040
• Main Authors: Zhang, Yu Ting, Chen, Mengyun, He, Shuiqing, Fang, Chao, Chen, Mingliang, Li, Dan, Wu, Dong, Chernick, Melissa, Hinton, David E., Bo, Jun, Xie, Lingtian, Mu, Jingli
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01-04-2021
• Subjects: Animals; Binary mixture; Larva; Locomotor activity; Marine medaka (Oryzias melastigma); Microplastics; Organophosphates - toxicity; Oryzias; Plastics - toxicity; Triphenyl phosphate; Water Pollutants, Chemical - analysis; Water Pollutants, Chemical - toxicity; Binary mixture; Microplastics; Marine medaka (Oryzias melastigma); Triphenyl phosphate; Locomotor activity
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2020.143040

Plastics have been recognized as a serious threat to the environment. Besides their own toxicity, microplastics can interact with other environmental pollutants, acting as carriers and potentially modulating their toxicity. In this study, the toxicity of polystyrene (PS) microplastic fragments (plain PS; carboxylated PS, PS-COOH and aminated PS, PS-NH2) and triphenyl phosphate (TPhP) (an emerging organophosphate flame retardant) at the environmentally relevant concentrations to the marine medaka (Oryzias melastigma) larvae was investigated. Larvae were exposed to 20 μg/L of microplastic fragments or 20 and 100 μg/L of TPhP or a combination of both for 7 days. The results showed that the three microplastics did not affect the larval locomotor activity. For TPhP, the larval moving duration and distance moved were significantly decreased by the TPhP exposure, with a maximum decrease of 43.5% and 59.4% respectively. Exposure to 100 μg/L TPhP respectively down-regulated the expression levels of sine oculis homeobox homologue 3 (six3) and short wavelength-sensitive type 2 (sws2) by 19.1% and 41.7%, suggesting that TPhP might disturb eye development and photoreception and consequently the low locomotor activity in the larvae. Interestingly, during the binary mixture exposure, the presence of PS, PS-COOH or PS-NH2 reversed the low locomotor activity induced by 100 μg/L TPhP to the normal level. Relative to the larvae from the 100 μg/L TPhP group, the movement duration and distance moved were increased by approximately 60% and 100%, respectively, in the larvae from the TPhP + PS, TPhP + PS-COOH and TPhP + PS-NH2 groups. However, the gene expression profiles were distinct among the fish from the TPhP + PS, TPhP + PS-COOH and TPhP + PS-NH2 groups, implying different mechanisms underlying the reversal of the locomotor activity. The findings in this study challenge the general view that microplastics aggravate the toxicity of the adsorbed pollutants, and help better understand the environmental risk of microplastic pollution.
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•Microplastics (PS, PS-COOH and PS-NH2) at 20 μg/L do not alter the locomotion in the larvae.•TPhP at 20 and 100 μg/L suppresses the locomotor activity in the larvae.•TPhP at 20 and 100 μg/L might disturb the eye development and photoreception of the larvae.•Microplastics alleviate the TPhP-induced toxicity in the larval locomotor activity.•The gene expression patterns induced by TPhP in the presence of PS, PS-COOH and PS-NH2 are distinct.