Invisible Trace Evidence: Using Environmental DNA (eDNA) to Detect Species in Aquatic Ecosystems

Environmental DNA is an innovative method to collect accurate data is needed to predict presence of species at risk and other species that use aquatic habitats for impact assessment, meet regulatory requirements and identify specific mitigation to address potential adverse effects. This method is particularly suited to linear transportation projects which typically cross or impact multiple waterbodies.
In British Columbia, federal and provincial guidance require stringent sampling methods to demonstrate presence / absence of species at risk. Trapping and other direct sampling methods can have significant impacts on the target species (e.g., mortality). As organisms shed deoxyribonucleic acid (DNA) in aquatic environments, eDNA samples can be collected from these environments. Studies of eDNA have gained scientific and regulatory acceptance in recent years, especially for surveying at-risk aquatic and semi-aquatic species. Benefits of this type of sampling include:
• Lower costs - eDNA field sampling requires only the collection of water samples, avoiding complex multi-day conventional sampling programs (e.g., baited trapping, electro-shocking and/or physical searches. Once baseline primer development is complete, costs can be 10% or less of conventional
methods.
• Non-invasive – avoids mortality risk due to physical injury or pathogen transfer associated with conventional methods
• Highly accurate – eDNA sampling when correctly implemented, is definitive for detection of presence and very sensitive to detection of aquatic species;

The credibility of eDNA survey data, however, depends on adequate methodological validation and verification; accurate results require rigour during field sampling, sample processing, laboratory analysis, and primer design and/or verification. Hemmera recently developed accepted standards for collection of eDNA for the BC Ministry of Environment and has completed for multiple transportation projects including MOTI’s South Fraser Perimeter Road (target species - red-legged frog and Pacific water shrew), MOTI’s Kicking Horse Canyon Phase 4 (target species Western toad) and TransLink’s Surrey Langley SkyTrain project (target species – multiple salmonids, Pacific water shrew and red-legged frog).