Using eDNA, biologists reveal a river’s creatures

In western Montana rivers, researchers are revolutionizing wildlife biology using “environmental DNA,” or eDNA. The method allows scientists to quickly and cheaply detect every creature that has been in a stream over the previous two days.

Determining the presence of different species in aquatic environments has been a time-consuming, costly and inexact task. But now, with just a small water sample, the eDNA approach can identify the presence of species from sloughed-off skin, bodily fluids or feces that fish, insects and animals continually leave behind. The approach can detect wildlife up to a kilometer upstream from where a water sample is taken.

Woman collecting sample from river (U.S. Forest Service)
U.S. Forest Service researcher Kellie Carim prepares a filter with collected DNA samples. (U.S. Forest Service)

“Environmental DNA is turning out to be an amazing tool in allowing us to detect the distribution of species, a distribution that has been invisible to us in the past,” said Michael K. Schwartz, director of the U.S. Forest Service’s National Genomics Center for Wildlife and Fish Conservation in Montana. “It has remarkable efficiency,” he told Yale Environment 360, an online publication from Yale University.

eDNA detects endangered animals or organisms and identifies species that are not native to an area — species that could cause damage to an ecosystem.

“You can’t manage a species if you don’t know where it is — even 80-pound Asian carp, because you can’t see them underwater,” said Cornell University biologist David Lodge. “So eDNA is particularly powerful in aquatic systems.”

The low cost of eDNA testing, between $50 and $150 to examine each sample, is significantly less than the cost of traditional monitoring methods.

The U.S. Forest Service is collecting DNA from rivers and streams across the western U.S. to create an Aquatic Environmental DNA Atlas.

Experts say that as the technology improves, it could be applied to ocean environments.