Contaminant‐Driven Modulation of Environmental DNA and RNA in Aquatic Systems

ABSTRACT Metals and microplastics rank among the most concerning contaminants in aquatic environments due to their persistence, ubiquity, and impacts on ecosystem stability and living organisms' health. The use of environmental DNA and environmental RNA (also called eDNA and eRNA) for biomonitoring has been suggested to assess the effects of these contaminants on aquatic species distribution, behavior, and/or health. However, understanding the impact of contaminants directly on the ecology of environmental nucleic acids (eNAs) could lead to a better interpretation of the data during monitoring surveys in polluted environments. In this study, we assessed the influence of lead (Pb) and polyethylene (PE) microbeads on both eDNA and eRNA production and persistence in juvenile landlocked salmons ( Salmo salar ) and American eels ( Anguilla rostrata ) through a series of controlled laboratory experiments. Data show no effect of Pb on eNA production following an exposure of 48 h at a concentration of 0.1 mg/L. The persistence was not affected either by this metal. On the other hand, exposure of fish individuals to 1 mg/L of PE microbeads led to increased eRNA levels during the production phase, which may be associated with an upregulation of genes associated with a generalized stressing event. Microplastics also led to a slower degradation of eNA molecules, allowing a longer persistence of the genetic material in aquatic ecosystems. Further investigations are needed to fully understand the direct and indirect interactions between contaminants and environmental nucleic acids. Thus, this would allow a better interpretation of the data during monitoring surveys, especially in contaminated environments.