What a Glass of Seawater Can Tell Scientists About the Health of the World’s Oceans

New genetic sequencing technology allows biologists to detect endangered species from the DNA they leave behind.

(Photo: Jorge Silva/Reuters)

Jul 5, 2014· 1 MIN READ
Katharine Gammon has written for Nature, Wired, Discover, and Popular Science. A new mom, she lives in Santa Monica.

As the cost of DNA sequencing plummets, scientists are now decoding the genetic mysteries of the world’s oceans to detect the presence of endangered species and calculate the impact of pollution and climate change on marine life.

All that data can be contained in a glass of seawater.

Environmental DNA—or eDNA—can serve as fast and inexpensive way to monitor the health of ecosystems, according to scientists who published a paper on the technique this week in the journal Science.

It works like this: Organisms, be they blue whales or microscopic plankton, shed DNA over time, contributing to an ocean of genetic information. By counting exactly how much genetic material is present in seawater, scientists can determine which species are nearby, as well as the number of individuals in each species. The technique has successfully identified creatures living as far as a kilometer away from the sampling site.

“eDNA allows us to ask questions like: Is there an endangered species or an invasive species present?” said Ryan Kelly, a biologist and assistant professor at the University of Washington, who coauthored the paper.

The scientists have demonstrated that eDNA techniques were able to identify most of the 13,000 fish in a 1.2 million–gallon tank at the Monterey Bay Aquarium.

Kelly said he hopes such genetic technology will become part of the toolkit for environmental monitoring in the years ahead. It certainly has become cheaper. In 2001, it cost $5,300 to sequence a water sample. The price today? Six cents.

The technology is already being deployed as an early-warning system to detect Asian carp in the Great Lakes. But eDNA could also be used on land, to identify pathogens in the soil, for instance, Kelly said.

For now, though, the focus is on the oceans. The Monterey Bay Aquarium Research Institute uses a device called the Environmental Sample Processor, or ESP. A buoy deployed in Monterey Bay contains a processor that analyzes genetic information in seawater. It currently examines ocean-going bacteria but could be used to detect the presence of larger marine species.

“It’s kind of like a water-bound R2D2 monitoring and doing real-time analysis of DNA,” Kelly said. “What’s exciting about eDNA is that it may offer a high-resolution snapshot of what is where, in a way that we haven’t had before.”