Multi-species eDNA as a screening tool to facilitate early detection and eradication of aquatic invasive species in large water bodies

Aquatic invasive species can devastate native biodiversity and human water infrastructure. Effective eradication relies on early detection. However, commonly used visual surveys are ineffective for detection of small populations of submerged invasive species in large water bodies. Here, we explored detection of invasive aquatic plants, animals (vertebrate and invertebrate), and pathogens using 10 environmental DNA (eDNA) water sampling events every two weeks between June and October, 2018, informing ideal sampling times for long-term early-detection monitoring. The highest number of species detections across taxa were found using 6 replicates in late August and early September. Detections varied by taxon, with the most detections for fishes, followed by invertebrates, amphibians, and submerged plants. All expected species were detected with eDNA except for three terrestrial and emergent riparian plants. Reservoirs had the most consistent presence of AIS, suggesting that those systems and aquatic communities may be susceptible to new invasions. AIS detections occurred across more sites and water bodies than had been previously documented which provided evidence of silent invasions by species such as crayfishes, mollusks, and plants. We offer a framework for interpreting management response to low-read counts from multispecies eDNA sampling that balances interpretation of results with the cost of management responses.