Environmental DNA (eDNA)

Environmental DNA (eDNA) analyses encompass a rapidly advancing set of methods to efficiently detect the presence of species by detecting the presence of their unique DNA signatures in environmental samples of water, sediments, soils, and other media. Analysis of eDNA can be used for the targeted surveillance of specific species and for characterizing entire communities within a habitat. Studies using eDNA can provide insight into the presence of rare and endangered species or difficult to sample organisms, detect invasive species before populations grow out of control, reconstruct historical populations, and assess and compare communities. Remote or hazardous areas that are difficult to sample using conventional methods may be more readily assessed using eDNA.

Our team of environmental genetic experts at Exponent are prepared to use eDNA to detect species occupancy and evaluate changes in ecological communities in response to hazardous substances releases (e.g., oil spills, wastewater), infrastructure development (e.g., off-shore wind energy, natural and nature-based features), agriculture (e.g., pesticides application, off-shore aquaculture development), bacterial and pathogen source tracking, and many other issues. Exponent staff have designed and conducted eDNA sampling and analyses, assessed laboratory protocols, and developed ecological models necessary to appropriately interpret eDNA studies and provide valuable insights to clients making crucial environmental decisions.

The detection of species using eDNA has numerous benefits that can complement traditional sampling techniques:

  • eDNA is sensitive to the presence of species at low abundance or density, such as rare species, recently introduced or invasive species, cryptic or morphologically difficult to identify species, and elusive or trap-shy species, thus providing species and community data that cannot be captured using traditional survey techniques.
  • eDNA sampling is non-invasive, non-destructive, and can be conducted with minimal disturbance and little risk to both sensitive and protected species as well as field assessors. Sampling can be conducted remotely, including using unmanned aerial or underwater vessels.
  • eDNA detections are time and cost-efficient, requiring less time and field effort than traditional data collection methods. Advanced, next-generation genomic technologies allow processing of multiple samples across multiple sites simultaneously, with hundreds or even thousands of individual species detections.
  • eDNA can be obtained from sediment cores and provide a window into historical conditions. Such information can be used to assess trends of species or communities over time or before an event.
  • eDNA methodologies are transparent. The physical samples, data, analysis software, and results may be readily archived for future re-analysis.
  • eDNA technology continues to advance, opening doors to additional applications.

Exponent is leading the application of eDNA techniques in decision-making and regulatory contexts to provide reliable, actionable ecological knowledge, and we understand the limitations and uncertainties associated with using these evolving methods. Limitations of using eDNA based analyses previously identified by our experts include the uncertainties in the physical processes that influence the preservation and degradation of eDNA, detection errors arising from laboratory processing, and developing statistical techniques to make inferences about species occurrence and community structure. Incorrect understanding of the limitations of eDNA can produce erroneous estimates of species presence or absence, ultimately leading to unsupported actions. Exponent specializes in identifying and managing uncertainties through the careful design and review of eDNA assays, assembling best-practices and protocols following advances in the latest research, bioinformatic statistical modeling, and clear communication of results. Currently, we are actively assessing the appropriate use of comparative controls and the adequacy of reference sites as well as the use of eDNA analyses to inform natural resource damage assessment (NRDA) and provide supportable descriptions of baseline.

New eDNA techniques and advances in genetic technologies, driven by research in human health, evolution, forensics, and myriad other fields, will continue to provide new and advancing methodologies for eDNA research, often faster than any particular method can be standardized and validated. Exponent can provide state-of-the-art technical expertise to assure that eDNA studies are appropriately designed and applied to better support the understanding and acceptance of eDNA based species and community assessments.

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