Effective management of rare species, including endangered native species and recently introduced nonindigenous species, requires the detection of populations at low density. For endangered species, detecting the localized distribution makes it possible to identify and protect critical habitat to enhance survival or reproductive success. Similarly, early detection of an incipient invasion by a harmful species increases the feasibility of rapid responses to eradicate the species or contain its spread. Here we demonstrate the efficacy of environmental DNA (eDNA) as a detection tool in freshwater environments. Specifically, we delimit the invasion fronts of two species of Asian carps in Chicago, Illinois, USA area canals and waterways. Quantitative comparisons with traditional fisheries surveillance tools illustrate the greater sensitivity of eDNA and reveal that the risk of invasion to the Laurentian Great Lakes is imminent.

Environmental DNA (eDNA) surveillance holds great promise for improving species conservation and management. However, few studies have investigated eDNA dynamics under natural conditions, and interpretations of eDNA surveillance results are clouded by uncertainties about eDNA degradation. We conducted a literature review to assess current understanding of eDNA degradation in aquatic systems and an experiment exploring how environmental conditions can influence eDNA degradation. Previous studies have reported macrobial eDNA persistence ranging from less than 1 day to over 2 weeks, with no attempts to quantify factors affecting degradation. Using a SYBR Green quantitative PCR assay to observe Common Carp ( Cyprinus carpio ) eDNA degradation in laboratory mesocosms, our rate of Common Carp eDNA detection decreased over time. Common Carp eDNA concentration followed a pattern of exponential decay, and observed decay rates exceeded previously published values for aquatic macrobial eDNA. Contrary to our expectations, eDNA degradation rate declined as biochemical oxygen demand, chlorophyll, and total eDNA (i.e., from any organism) concentration increased. Our results help explain the widely divergent, previously published estimates for eDNA degradation. Measurements of local environmental conditions, consideration of environmental influence on eDNA detection, and quantification of local eDNA degradation rates will help interpret future eDNA surveillance results.

With increasing pressure placed on natural systems by growing human populations, both scientists and resource managers need a better understanding of the relationships between cumulative stress from human activities and valued ecosystem services. Societies often seek to mitigate threats to these services through largescale, costly restoration projects, such as the over one billion dollar Great Lakes Restoration Initiative currently underway. To help inform these efforts, we merged high-resolution spatial analyses of environmental stressors with mapping of ecosystem services for all five Great Lakes. Cumulative ecosystem stress is highest in nearshore habitats, but also extends offshore in Lakes Erie, Ontario, and Michigan. Variation in cumulative stress is driven largely by spatial concordance among multiple stressors, indicating the importance of considering all stressors when planning restoration activities. In addition, highly stressed areas reflect numerous different combinations of stressors rather than a single suite of problems, suggesting that a detailed understanding of the stressors needing alleviation could improve restoration planning. We also find that many important areas for fisheries and recreation are subject to high stress, indicating that ecosystem degradation could be threatening key services. Current restoration efforts have targeted high-stress sites almost exclusively, but generally without knowledge of the full range of stressors affecting these locations or differences among sites in service provisioning. Our results demonstrate that joint spatial analysis of stressors and ecosystem services can provide a critical foundation for maximizing social and ecological benefits from restoration investments.Laurentian Great Lakes | cumulative impact | marine spatial planning | fresh water

Three mantras often guide species and ecosystem management: (i) for preventing invasions by harmful species, ‘early detection and rapid response’; (ii) for conserving imperilled native species, ‘protection of biodiversity hotspots’; and (iii) for assessing biosecurity risk, ‘an ounce of prevention equals a pound of cure.’ However, these and other management goals are elusive when traditional sampling tools (e.g. netting, traps, electrofishing, visual surveys) have poor detection limits, are too slow or are not feasible. One visionary solution is to use an organism’s DNA in the environment (eDNA), rather than the organism itself, as the target of detection. In this issue of Molecular Ecology, Thomsen et al. (2012) provide new evidence demonstrating the feasibility of this approach, showing that eDNA is an accurate indicator of the presence of an impressively diverse set of six aquatic or amphibious taxa including invertebrates, amphibians, a fish and a mammal in a wide range of freshwater habitats. They are also the first to demonstrate that the abundance of eDNA, as measured by qPCR, correlates positively with population abundance estimated with traditional tools. Finally, Thomsen et al. (2012) demonstrate that next-generation sequencing of eDNA can quantify species richness. Overall, Thomsen et al. (2012) provide a revolutionary roadmap for using eDNA for detection of species, estimates of relative abundance and quantification of biodiversity.

Environmental DNA (eDNA) is a sensitive technique for early detection of rare species, including bighead (Hypophthalmichthys nobilis) and silver (Hypophthalmichthys molitrix) carp, which are incipient invaders of the Great Lakes. Since 2009, 2822 samples have been collected from the Great Lakes basin to delimit the extent of Asian carp incursions. Samples collected in the Chicago Area Waterway System and in the western basin of Lake Erie indicate the presence of Asian carp DNA in the Great Lakes. These positive eDNA detections are within 6 and 4 km from where bighead carps were recovered in Lake Calumet, near Lake Michigan (2010), and from Sandusky Bay, Lake Erie (2000), respectively. To implement a Great Lakes surveillance plan for protecting imperiled species and reducing damages from invasive species, federal, state, and provincial agencies will need to cooperatively plan and implement a surveillance program that employs the unique strengths of multiple sampling tools, including eDNA methods.