Environmental DNA surveillance of biocontamination in a drinking water treatment plant.

A clean and adequate supply of drinking water is essential to life and good health. However, despite the risk of biologically derived contamination of drinking water, monitoring of invertebrate outbreaks has relied primarily on naked-eye inspections that are prone to errors. In this study, we applied environmental DNA (eDNA) metabarcoding as a biomonitoring tool at seven different stages of drinking water treatment, from prefiltration to release from household faucets. While the composition of invertebrate eDNA communities reflected the communities of the source water in earlier stages of the treatment, several predominant invertebrate taxa (e.g., rotifer) were shown to be introduced during purification, but most were eliminated in later treatment stages. In addition, the limit of detection/quantification of PCR assay and read capacity of high-throughput sequencing was assessed with further microcosm experiments to estimate the applicability eDNA metabarcoding to the biocontamination surveillance in drinking water treatment plants (DWTPs). Here we propose a novel eDNA-based approach for sensitive and efficient surveillance of invertebrate outbreaks in DWTPs.

Metabolism deficiency and oxidative stress induced by plastic particles in the rotifer Brachionus plicatilis: Common and distinct phenotypic and transcriptomic responses to nano- and microplastics.

Growing experimental data on the adverse effects of microplastic pollution on marine biota indicate that the size of the plastic particles is a key determinant of toxicity. Here, we investigated size-dependent toxicity at different levels of biological organizations in the marine rotifer Brachionus plicatilis, from bioaccumulation as an initiating event to adverse in-vivo outcomes, with ecotoxicogenomic approach to elucidate the size-dependent toxicity of microplastics. Nanoplastics strongly retarded the reproduction and population growth of B. plicatilis, while microplastics were associated with moderate effects. This size dependency could be attributed to the selective induction of oxidative stress by nanoplastic exposure in addition to a metabolic deficiency, which was a common toxicity mechanism with both nano- and microplastic exposure as predicted by transcriptomic analysis. Our findings suggested that metabolic deficiency is a shared toxicity mechanism of nano- and microplastics, while oxidative stress might be responsible for the stronger toxicity of nanoplastics.

Phenotypic toxicity, oxidative response, and transcriptomic deregulation of the rotifer Brachionus plicatilis exposed to a toxic cocktail of tire-wear particle leachate.

Tire-wear particles (TWPs) are potential source of microplastic (MP) pollution in marine environments. Although the hazardous effects of MPs on marine biota have received considerable attention, the toxicity of TWPs and associated leachates remain poorly understood. Here, to assess the toxicity of TWP leachate and the underlying mechanisms of toxicity, the phenotypic and transcriptomic responses of the rotifer Brachionus plicatilis were assessed with chemistry analysis of a TWP leachate. Although acute toxicity was induced, and a variety of metals and polyaromatic hydrocarbons were detected in the leachate, levels were below the threshold for acute toxicity. The results of particle analysis suggest that the acute toxicity observed in our study is the result of a toxic cocktail of micro- and/or nano-sized TWPs and other additives in TWP leachate. The adverse effects of TWP leachate were associated with differential expression of genes related to cellular processes, stress response, and impaired metabolism, with further oxidative stress responses. Our results imply that TWPs pose a greater threat to marine biota than other plastic particles as they constitute a major source of nano- and microplastics that have synergistic effects with the additives contained in TWP leachate.

Effects of atrazine and diuron on life parameters, antioxidant response, and multixenobiotic resistance in non-targeted marine zooplankton.

Atrazine and diuron are among the most widely used antifoulant biocides in the world. Due to their persistence in the environment, they can induce adverse effects on non-targeted organisms. In this study, we investigated the chronic in vivo toxicity of atrazine and diuron with further assessments on oxidative stress responses (e.g., oxidative stress, antioxidant) and multixenobiotic resistance (MXR) function in the rotifer Brachionus koreanus, a non-targeted microzooplanktonic grazer at the primary level of the marine food chain. Although similar oxidative response was shown by both biocides, diuron induced stronger retardation on reproduction and population growth rates of B. koreanus while moderate effects were observed by atrazine. This higher toxicity of diuron was shown to be associated with its stronger inhibition of MXR conferred by P-glycoprotein and multidrug resistance proteins which play as a first line of defense by transporting various toxicants out of a cell. Our study provides new insight into non-targeted effects of biocides on marine zooplankton and mechanisms beyond their different degrees of toxicity.