Each summer, many beaches along the Great Lakes are shut down because the waters have high bacteria levels. But figuring out exactly when to close a beach is difficult, and scientists are trying out a new test that could lead to safer swimming.
Each of the eight Great Lakes states has some way to track contamination. That’s important because polluted water can cause infections and illnesses, including gastroenteritis. Children and elderly people are most at risk. To check on water quality, one of the most popular tests is called Colilert .
On a recent morning in Cleveland, a Northeast Ohio Regional Sewer District intern waded in to test the water at Villa Angela – Euclid Beach.
Lindsay Baker, another intern, described the process at the beach, one of three that the agency tests: “We come out, we take a bacteria sample, we take turbidity sample, and bring them back for each beach and send them to the lab where they get tested for E. coli."
Colilert measures E. coli, a type of bacteria that indicates conditions that can make you sick. But while the Colilert test is used widely, it takes 18 -24 hours to get a result.
“You don’t have your results for today until tomorrow,” said Nicole Shafer, a microbiologist with the sewer district. “That doesn’t do you much good if you want to go to the beach today.”
In addition to testing water quality using Colilert, the agency uses predictive models to make a same-day announcement . The model is created from past data, including wave height and precipitation.
But as the agency’s Mark Citriglia explains, the predictive model still isn’t completely accurate.
“We’re probably around 78 percent accurate,” said Citriglia. “Using the previous day’s E. coli is really about 60% accurate, so we’re much better than that.”
Some agencies use predictive models, but others are using old, less accurate data to make judgements on whether it’s safe to swim at the beach.
Now the sewer district and agencies in 5 other states are experimenting with a faster test. Citriglia says it uses bacterial DNA to test water quality.
“We look for a specific DNA, we replicate the DNA, we can get results in four hours,” he said. “We’re finding that to be more accurate than the predictive model.”
This technique is called qPCR, which stands for quantitative polymerase chain reaction. Citriglia uses it to measure E. coli, and it can lead to quicker and more accurate measurement of fecal contamination, letting beachgoers know if it’s safe to swim or not.
qPCR may lead to even more information, like the specific sources of contamination, says Schafer. “We can determine in the lake, in the beaches, in storm water runoff: Where is the contamination coming from? We’ll be able to test. Is it coming from dogs? Is it coming from humans? Geese, chicken, gulls, ducks?”
It’s all about different kinds of bacteria. Though E. coli is used to test water quality, a bacteria called bacteroides is used to distinguish possible contamination sources.
“Every single living creature has a slightly different bacteroides in their gut,” said Schafer. It’s almost like a fingerprint.
The sewer district is one of 23 labs participating in a study to evaluate the qPCR method for E. coli testing. Four Great Lakes states are involved -- Ohio, Michigan, Illinois, and Wisconsin – as well as Georgia and North Carolina. The results will be released next month.
If the U.S. Environmental Protection Agency endorses the qPCR test, beachgoers will get better, quicker information about the health risks of the Great Lakes.
But it’ll be even longer before we find out what’s contaminating the beaches. Citriglia says it will take two years to gather enough data to differentiate each source of contamination at the beaches.