LONG BRANCH — One container of crystal-clear water can reveal quite the story for marine researchers at Monmouth University.

Advances in technology allow researchers, and students, to detect the recent presence of marine life such as sharks and fish, just by dunking an empty jug into the ocean or bay and capturing the animals' environmental DNA (eDNA) left behind. With the process, netting or physically spotting a creature isn't necessary to determine what's been swimming in New Jersey's waters and when.

"When a fish or whale swims through the water, they're constantly sloughing off skin cells, or defecating, and that material contains those pieces of DNA from that animal," said Jason Adolf, an endowed professor of marine science who designs and performs the eDNA sampling.

Invisible to the naked eye, the DNA shed by species can last in the water for 48 to 72 hours, Adolf said. That short shelf life is considered a good thing; when researchers detect eDNA, they know it's related to a species that's been in the vicinity within the past few days.

"What eDNA is offering is basically another way of looking beneath the water to see what's there, using molecular technology instead of net technology," Adolf said.

The non-destructive, non-invasive practice is considered a low-cost alternative to other methods of sampling marine life, and holds up in foul weather. The sampling itself is so simple, Adolf said, it opens the door to a potential citizen science component in the future.

"If you have the pipeline for analysis, people all over the place can be collecting bottles of water and having them analyzed," Adolf said, noting most samples look as clean and clear as drinking water when pulled from the ocean.

Researchers are currently working with the New Jersey Department of Environmental Protection to compare eDNA data with information gathered through the state's trawling methods. The presence of a fin whale, for example, wouldn't be detected in a trawl, but it may leave plenty of eDNA behind for Adolf and company.

Adolf noted eDNA readings cannot determine the abundance of a species. The technology also cannot determine whether the eDNA was shed by a living animal or one that just died, the university said.

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