Aquatic ecosystems, such as waterways, wetlands and lakes, are often sinks for contaminants that enter the environment from anthropogenic activities and extreme climate events. The presence of contaminants potentially harmful to both human health and ecosystem function is currently being measured primarily by chemical properties of water and bacterial culture-based approaches. However, impacts of contaminants, as well as biological risks such as pathogenic bacteria, can also be measured from the same samples by environmental DNA (eDNA), complementing traditional approaches. Routine collection of biological data in toxicity studies is a crucial next step in understanding the response of individual species, and biodiversity in general, to human activities and events, to inform future management and responses.
Here we present three case studies applying eDNA to help understand contamination risks and impacts in aquatic ecosystems, including (1) the assessment of potential anthropogenic microbial pollution in floodwaters; (2) measuring background sewage contamination conditions and undertaking source tracking to inform future management and investment; and (3) using comprehensive, landscape-scale baseline data to assess the impact and recovery of emergency discharge and pollution events.