Each summer, many beaches along the Great Lakes are closed because of high bacteria levels in the water. 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, which is important because polluted water can cause infections and illnesses, like gastroenteritis. Children and elderly people are most at risk. But to check the water quality is one of the most popular tests 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," Baker said.
Colilert tests for E. coli, a type of bacteria that indicates conditions that can make you sick. However, this can take 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 percent accurate, so we’re much better than that.”
Some agencies use predictive models, but others are using old, less accurate data to make judgments on whether it’s safe to swim at the beach.
Now, the sewer district and agencies in five 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. The qPCR test still measures E. coli, but can lead to a quicker and more accurate measurement of fecal contamination, letting beachgoers know if it’s safe to swim or not.
The qPCR technique 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?” Schafer said.
It’s all about different kinds of bacteria. Although 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 also 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 will 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.