Whether it's in sloughed skin, feces or other biological substances, animals regularly cast off bits of their DNA into aquatic environments. Known as environmental DNA (eDNA), it can be detected in water samples, letting scientists know if a given species is present in the region. Soon, it could be used to warn beachgoers of nearby great white sharks.

The concept is being developed through a collaborative research project involving scientists from the University of California Santa Barbara, the US Geological Survey, California State University Long Beach and Central Michigan University.

In initial studies, UC Santa Barbara's Kevin Lafferty and colleagues had difficulty detecting great white eDNA in areas where the animals were suspected of being present. The scientists then turned to a lab-based genetic analysis technique known as digital droplet PCR, which allowed them to identify species-specific genetic markers (DNA sequences) within samples of great white shark tissue.

When a student subsequently looked for those markers in water samples drawn from different areas of the ocean, they were able to correctly determine which sample came from a region where the sharks were gathered, and which came from a region one mile away, where no sharks were present. Ultimately, it is hoped that the technology could one day allow lifeguards to simply take and analyze water samples at the beach, to see if any great whites were in the area.

That said, due to the fact that shark eDNA can be carried considerable distances by currents (and the fact that sharks can swim long distances after releasing eDNA), such a setup wouldn't let users know precisely where the sharks were. To that end, Lafferty envisions a system in which autonomous aquatic surface drones could analyze the water from a variety of locations, transmitting their data to the cloud for analysis. If a shark were detected in a given area, lifeguards could be notified via text alerts.

A paper on the research was recently published in the journal Frontiers in Marine Science.

eDNA analysis has also been used to search for frog fungus, invasive clams, migratory fish and even the Loch Ness monster.