One in four freshwater organisms are currently at risk of extinction, but saving aquatic species can be more difficult than conserving their land-based counterparts as they are inherently less visible to the human eye and less accessible to researchers. To address this, scientists ​​Marie Simonin and Emily S. Bernhardt are turning to biomonitoring as a way to quantify and improve the health of freshwater ecosystems.

Using environmental DNA, or eDNA, they can assess population numbers and species prevalence—even when the species in question may be invisible to the naked eye. The researchers and their team extract eDNA from genetic material floating in the water like skin, scales, waste, and bacteria. Using this data, they can identify the presence of a wide range of species and pin down whether an at-risk species frequents the particular ecosystem.

From just a four-ounce water sample, Simonin and Bernhardt can look for evidence of bacteria, algae, fish, and macroinvertebrates one by one. Matching this DNA evidence to samples in their lab, the researchers come up with a distribution chart identifying the abundance of each organism in the sampled region. In addition to offering insights into difficult-to-spot species, the method also doesn’t require harming any of the individual organisms and is relatively inexpensive.

The researchers and their team have used this method to survey 93 rivers in West Virginia, tallying more than 10,000 different species just in these waters. As a heavy coal-mining region, the team was also able to identify how these extraction operations affect local aquatic life and identify that mined watersheds have 40 percent fewer species than undisrupted habitats.

The researchers note that while traditional ecosystem monitoring methods still have valuable applications, eDNA methods save considerable time, effort, and funds, plus, the open-source nature of DNA data means that nearly any research team can tap into this collective knowledge base.