By Gabe Pelletier, Project Technician and Jake Riley, Associate, Stantec
What do human beings, Zebra mussels, and Atlantic salmon have in common? They all contain deoxyribonucleic acid (DNA) in each cell. DNA is the molecule that contains the genetic code for each organism. All living organisms expel this unique genetic material into their environment, and we call this material “environmental DNA” (eDNA). Currently our planet is facing a biodiversity challenge with regards to rare, threatened, and endangered species and a simultaneous increasing threat of invasive species. Maine has a combination of approximately 60 State and Federally listed threatened and endangered animal and invertebrate species. When considering the development of a property or project, the planning process may require studies to determine if these species could be affected. Presence of these species could require permitting, compensation for impacts to habitat, or costly changes to project plans. Now, more than ever, it’s increasingly important to find effective, rapid, and efficient ways to monitor where these species are to meet regulatory requirements for protection, as well as to design projects that reduce or avoid impacts to protected species and manage invasive species.
In aquatic settings, fish and other aquatic species (e.g. amphibians) shed eDNA through the skin, feces, urine, blood, body, eggs, or sperm into the water they inhabit. eDNA emitted from species can be detected by filtering a water sample taken directly from a water body, extracting the eDNA, and the eDNA is analyzed to detect the presence of a specific target species.
How does eDNA stack up against more conventional methods for observing and detecting aquatic species, such as trapping, netting, and/or electrofishing? In short, conventional methods may take additional time, be more expensive, and could harm rare species and their habitat while requiring a state collection permit. Conventional sampling techniques often require a visual detection of the target species to determine presence versus a positive detection from the presence of the target species eDNA.. This eDNA survey technique can extend the survey season, make it possible to survey migratory species, survey vernal pools outside the spring breeding window, survey for elusive species and species at low densities, and survey life stages (e.g. eggs, larvae) and in conditions not previously possible with conventional equipment. Utilizing eDNA, biologists can prolong the traditional surveying period allowing for a larger sample size and a longer sampling season at potentially a lower cost to the developer.
Detecting eDNA in the aquatic environment depends on several factors when setting up a sampling design. The strength of the eDNA signal will depend on how recent the target species was present and how long the species was there. Population density and lifecycle stage also influence how much eDNA is present in the water body. Lastly, the volume and flow rate of the aquatic environment plays an important role for dictating the sampling design. Whereas a small pond or lake will likely hold eDNA longer, a running river is more likely to transfer remnant eDNA downstream.
The future for eDNA is bright and the applications are seemingly endless. Here in Maine we face environmental concerns not only in our inland and coastal water bodies, but also in rural and urban ecosystems. Using this new technology, tests are continuously being developed for aquatic species as well as expand to terrestrial species. The enthusiasm isn’t only in the scientific world, however, as this new surveying tool offers a way for developers to meet their regulatory requirements effectively and efficiently while reducing costs and avoiding harmful impacts to rare species.
Gabe Pelletier, Project Technician and Jake Riley, Associate can be reached by contacting Stantec’s Topsham, Maine office.