Environmental DNA breakthrough will aid conservation efforts

Forensics experts gather DNA to understand who was present at a crime scene. But what if the crime occurred in the middle of a lake, where DNA could be carried far and wide by wind and waves? That's the challenge faced by aquatic ecologists who study environmental DNA (eDNA) to monitor endangered animals, track invasive species, or monitor fish populations.

A team of ecologists and engineers from Cornell and the University of Granada has made a breakthrough in understanding eDNA movement in water. Researchers developed synthetic DNA that mimics the behavior of eDNA, released some of it in Cayuga Lake near Cornell's Ithaca campus, traced its movement for 33 hours, then incorporated their findings into a new model that can predict where a sampled particle of eDNA likely originated in a water body.

The research was published Jan. 20 in Environmental Science & Technology.

"Over the past 15 years, advances in molecular methods have expanded eDNA from single-species detection to community-wide biodiversity monitoring, often making it faster, cheaper and more sensitive than traditional survey methods," said Jose Andrés, paper co-author and senior research associate in the College of Agriculture and Life Sciences (CALS). "One of the key challenges, especially in large freshwater and marine environments where eDNA may be mixed quite deeply into the water column and currents may be strong, is knowing when detected DNA was released by the source organism, and how far away the organism was."

The synthetic DNA tracer was created by Zeyu Li, paper first author and a doctoral student in the lab of Dan Luo, another co-author and professor of biological and environmental engineering. The synthetic DNA tracer was made up of short and unique DNA sequences and then encapsulated in a safe, biodegradable polymer frequently used in the food and pharmaceutical industries. Only 1 microgram of DNA (one-thousandth of 1 gram) was released in the lake, he said.

"This paper was an exciting collaboration, especially because it has a real scenario of application," Li said. "This type of experiment could be repeated in Lake Ontario, or even the Atlantic Ocean - we have the capability of doing that. I believe that our technology is one that can make a real impact for the world."

The combination of expertise in genetics, biological engineering and ecology enabled researchers to study questions holistically and to make basic scientific advancements in multiple fields, said Todd Cowen, professor of civil and environmental engineering in Cornell Engineering and study co-author.

"High-dynamic-range studies of dispersion, fate and transport in these highly stirred and mixed aquatic environments is critical to managing our freshwater, estuarine and coastal marine resources," said Cowen, who is also a Cornell Atkinson faculty fellow and directs the DeFrees Hydraulics Lab. "This approach is a game changer."

Environmental DNA is a cheaper, faster, more accurate tool for fish and wildlife managers, as opposed to traditional survey practices like catching animals, said David Lodge, study co-author and the Francis J. DiSalvo Director of Cornell Atkinson. Lodge leads a nationwide effort to accelerate the adoption of eDNA in federal decision-making as chair of the Policy Subcommittee of the Marine Technology Society's Environmental DNA Committee. Regulators might use eDNA data to determine the environmental impact of an offshore energy installation, to track the population size of an endangered species, to see whether cargo ships are introducing invasive species or to assess the population of a commercially exploited fish species.

"You can't manage what you can't measure, and many traditional technologies for measuring biodiversity are hopelessly laborious, expensive or altogether infeasible," Lodge said. "The rapid loss of biodiversity in aquatic ecosystems requires effective, scalable tools to assess biodiversity and monitor change over time, and eDNA is certainly one of those tools."

Funding for this research came from the Cornell Atkinson Center for Sustainability and the U.S. Department of Defense.

Krisy Gashler is a writer for the Cornell Atkinson Center for Sustainability.