DNA Analysis Helps Identify Source Of Chattahoochee Bacteria | WABE 90.1 FM

DNA Analysis Helps Identify Source Of Chattahoochee Bacteria

Jun 26, 2017

This is not a story about the Chattahoochee River being super-filthy or anything like that – it's really not – but if you're planning a trip to the river, you may want to check its bacteria levels first.

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Most rivers and streams have bacteria in them. It's not all dangerous for humans, but some kinds can make people sick.

“Bacteria comes from a variety of sources,” U.S. Geological Survey ecologist Anna McKee said. “There are ducks in the water.”

Fecal coliform bacteria is part of nature, said McKee. It lives in animals' guts. Humans' guts, too. When they poop, the bacteria can end up in the water.

“There is always going to be bacteria there because there is wildlife that is contributing to fecal contamination in the Chattahoochee,” McKee said. “Whether or not that’s a severe human health risk, that has to do with bacteria levels.”

The Chattahoochee is monitored regularly for bacteria levels. The USGS works with the National Park Service and the Chattahoochee Riverkeeper to check for bacteria that can cause gastrointestinal issues, including e. coli and shigella. They post the information on their BacteriAlert website

McKee is working on research that goes a step beyond that.

USGS ecologist Anna McKee collects water samples from the Chattahoochee from a bridge above the river.
Credit Molly Samuel / WABE

Standing on a bridge over the river, right where the Chattahoochee flows under the Perimeter, McKee looked out at a couple people climbing into inner tubes. 

“This is a perfect example of one of the reasons we're doing these sample collections,” she said. “People are literally in the water. Several hours of exposure there.”

McKee dropped a plastic bottle into the river.

“What we're doing is collecting water samples to run a variety of tests to get an idea of bacteria levels, but we’re also trying to determine sources of these bacteria,” she said.  

Sources, as in, what kind of animal (or human) did the gut bacteria come from? Put another way: Whose poop is in this river?

With DNA analysis improving over the past decade, scientists can now figure out if the fecal coliform bacteria came from birds, or ruminants like deer or cows -- or from humans, which could suggest a sewer or septic leak nearby.

McKee says as the science gets better, they'll get a better sense of when the bacteria in the river really does pose a health problem, and how to address it.

For now, a bit of good news from the preliminary results. With bacteria from human guts, “We generally see higher levels during winter storm flow,” says McKee.

So not during the sunny summer weather when most people are in the Chattahoochee.