No abstract

Environmental DNA (eDNA) holds notable potential for biomonitoring and ecological research. However, its utility for quantifying temporal changes in abundance, biomass, and diversity remains contentious. We investigated biotic and abiotic factors influencing temporal variation in eDNA concentration in large, 28,000 L experimental mesocosms. Time series data demonstrated a positive relationship between the population abundance and biomass of the Cladoceran zooplankton species Daphnia magna and eDNA concentration, with a time lag of ~3.5 days in 25°C conditions, and up to 28 days in 15°C. Water temperature variations within mesocosms did not consistently influence eDNA quantity, although water temperature negatively predicted DNA concentration across mesocosms. Algal density negatively correlated with D. magna eDNA quantity across and within mesocosms. We demonstrate that eDNA signal detection can be used as a proxy for relative abundance and suggest that future investigation into the dynamics of eDNA shedding and degradation processes is warranted.

The fragmented ecosystems along the Niagara Escarpment World Biosphere Reserve provide important habitats for biota including lichens. Nonetheless, the Reserve is disturbed by dense human populations and associated air pollution. Here we investigated patterns of lichen diversity within urban and rural sites at three different locations (Niagara, Hamilton, and Owen Sound) along the Niagara Escarpment in Ontario, Canada. Our results indicate that both lichen species richness and community composition are negatively correlated with increasing human population density and air pollution. However, our quantitative analysis of community composition using canonical correspondence analysis (CCA) indicates that human population density and air pollution is more independent than might be assumed. The CCA analysis suggests that the strongest environmental gradient (CCA1) associated with lichen community composition includes regional pollution load and climatic variables; the second gradient (CCA2) is associated with local pollution load and human population density factors. These results increase the knowledge of lichen biodiversity for the Niagara Escarpment and urban and rural fragmented ecosystems as well as along gradients of human population density and air pollution; they suggest a differential influence of regional and local pollution loads and population density factors. This study provides baseline knowledge for further research and conservation initiatives along the Niagara Escarpment World Biosphere Reserve.

Early life stage (ELS) fishes provide a valuable metric for species, population, and ecosystem monitoring. Industrial, manufacturing, and power generating facilities in the United States can be required to monitor ELS fishes to assess impacts of facility intake waters.Traditional methods for collecting, identifying, and enumerating ELS fishes include ichthyoplankton netting and pumping from intake and discharge waters. However, sampling at these sites can prove challenging from logistical and safety standpoints, with added challenges of identifying and post-processing of ELS fishes to quantify facility impacts on waterbodies for regulatory purposes. Methods utilizing environmental DNA (eDNA) may offer improvements in these areas. This study assessed the utility of novel, species-specific qPCR assays to detect eDNA from three differentially abundant fish species (alewife (Alosa pseudoharengus; Wilson, 1811), gizzard shad (Dorosoma cepedianum; Lesueur, 1818), and yellow perch (Perca flavescens; Mitchill, 1814)) at the outflow of an industrial site. eDNA concentrations were compared with abundance estimates derived from two conventional collection methods to explore the potential utility of eDNA-based methods in future monitoring. The likelihood of detecting gizzard shad, yellow perch, and alewife in the discharge waters of the power generation station was not significantly different among eDNA, plankton netting, or pump sampling. Results suggest successful detections differ by species and time of year for each method.Gizzard shad eDNA relative abundance correlated strongly with total larval abundances captured by the pumping but not the netting methods, whereas yellow perch eDNA abundance was found to correlate with both conventional methods. Alewife was not detected by any method, consistent with documentation of the decline in this species within the lake. Overall, our study found a positive relationship between eDNA abundance and larval fish abundance in both daily and seasonal sampling, suggesting that fluctuations in eDNA concentration may be linked to larval abundance.

Brook trout are a species of conservation concern in Southwestern Ontario, Canada, and effective monitoring of their populations is crucial for making informed management decisions. Electrofishing is a traditional, yet invasive, method that allows for fish abundance estimation. Environmental DNA (eDNA) is an emerging molecular tool that presents a non-invasive alternative to electrofishing. This study was a collaborative effort between researchers in academia, industry, and an NGO, with the following objectives: 1) compare eDNA detections with electrofishing when monitoring brook trout populations in a site of known occupancy, 2) compare existing eDNA collection methods, and 3) extend eDNA surveys to regions of unknown occupancy that could be of conservation concern (Hanlon Creek and Twelve Mile Creek, Ontario). First, eDNA sampling methods were validated with standard electrofishing. Water samples were filtered in tandem at each site using two commercially available eDNA samplers. The results suggest a significant difference in total eDNA capture and incidence of PCR inhibitors between the two autosamplers. Brook trout eDNA was detected at all locations in Hanlon Creek in September and November, as well as 5/6 sampling locations in Twelve Mile Creek. Brook trout signal in Hanlon Creek was stronger in November compared to September 2019, suggesting possible spawning activity. Brook trout eDNA was also detected in Twelve Mile Creek where brook trout were previously unreported. This study provides a technical validation for the use of eDNA in brook trout monitoring and illustrates the opportunity to use eDNA surveys in regulated settings to complement and improve conventional biomonitoring methods for the management of elusive species.