Catalog number: USNM 142770 (Department of Invertebrate Zoology / Smithsonian Institution)

A new study used DNA gathered from stream water to confirm the presence of a tiny endangered crustacean within miles of the White House.

The Hay's Spring amphipod is only found in one place on earth: Rock Creek Park, a narrow, winding valley that cuts through the heart of Washington, DC. The shrimp-like animal is difficult to study: when scientists dig through leaves and rocks to look for it, they also destroy its habitat and to identify it, they need to take it back to the lab and kill it. Now scientists say they can detect small amounts of DNA left behind by the animal — proving it still exists even though it's rarely seen.

The solution: "We're shedding cells all the time. When we sneeze, when we breathe," Matthew Niemiller tells Axios. Niemiller is a cave biologist at University of Illinois Urbana-Champaign. These biological traces contain DNA, called environmental DNA or eDNA. By taking samples of water from streams near Rock Creek, Niemiller and his team were able to amplify the genetic fragments and prove that the amphipods still existed without harming their habitat. One limitation: eDNA can't tell how many animals are present, just that they are there.

Why it matters: "This study was a proof of concept to see if we could actually detect the species," says Niemiller. Hunting for eDNA isn't a new technique — microbiologists have been using it for years to find bacteria in soil. But now, biologists like Niemiller are using it for conservation and biodiversity research. He hopes to use this technique to look for species in hard-to-reach places like caves.

There are thought to be over seven million animal species on earth, only about one million of which have been identified. Daniel Fong, one of Niemiller's coauthors and a professor at American University, tells Axios he knows of at least fifteen possible new species of amphipod in North America alone, waiting to be confirmed and described.

The bottom line:

"Even here in our backyard, there's untapped biodiversity," says Niemiller. "Below ground is a place we haven't really explored at all. Things like flatworms, insects, there's a whole host of species and life that are not well known or well studied."

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