MOREHEAD CITY - The biggest danger facing beachgoers may not have fins, sharp teeth or even stinging tentacles. In fact, the biggest danger may be so small you can’t even see them. We’re talking about microbes that can give you stomach cramps, fever and nausea. After a storm, these microbes may be floating in the water with you.
While many microbes are found in the water naturally, stormwater runoff and sewage system failures can overwhelm coastal waters. A marine biologist has now developed a rapid water test to keep the public safe.
“There are really two sources of pathogens in the ocean,” says Dr. Rachel Noble, a Marine Microbiologist with the University of North Carolina Chapel Hill Institute of Marine Sciences. “There are pathogens in the ocean that are native to oceans, estuaries, lakes and rivers, they are naturally found there. But then after heavy rains, there are other, completely different pathogens like human viruses, that can be washed into the oceans, lakes and stream from the land, especially from stormwater runoff and sewage system overflows and failures.”
Those other pathogens have names: Norovirus, Enterovirus, Adenovirus and Salmonella.
Studies show almost 71% of the population lives within 100 miles of a coastline. That population density exponentially increases the amount of pollution that goes into the water.
“We have all of this infrastructure, sewage, septic systems, livestock, pets, and all of these things right on the coast,” adds Dr. Noble. “So no longer is dilution the solution to our pollution, we’ve got to consider the feedback loop. No longer are we impacting our environment. We are the recipients of those adverse impacts.”
To check for those adverse impacts, North Carolina’s Department of the Environment and Natural Resources tests 240 coastal beaches for microbial contaminants between April 1 and October 31. That’s considered the swimming season in the state. North Carolina always ranks high in beach water quality.
Still, in 2012, swimming advisories were issued for sections of 33 beaches in Beaufort, Brunswick, Carteret, Dare, New Hanover and Pamlico Counties. That’s about one percent of the state’s beaches. Most of the closings lasted for a week.
The current test involves taking water samples at the beach. The samples are taken back to a lab for analysis. However, it takes almost 24 hours to get results because any bacteria in the sample needs time to be allowed to grow. That means if a sample is taken on a Saturday morning there will not be a warning sign to close the beach, if the water proves to be dangerous, until Sunday morning.
Dr. Noble and her team have developed a quicker test that produces results in about three to four hours rather than 24.
“The organisms we test for are the same: Enterococcus, E Coli, and Fecal Coliform, that have been tested for by the EPA for decades,” says Dr. Noble. “The technology is slightly different.”
The test uses what’s called quantitative polymerase chain reactions, or qPCR for short.
It allows scientists to spot DNA from specific types of bacteria and then determine how much of that DNA is present. That’s the key, looking for DNA chains from specific bacteria of interest that can make people sick.
The water sample is run through a filter, which screens and traps the bacteria. For example, the filter for Enterococcus has holes that are point four microns in size. The filter holding the bacteria is then put into a vial, which is sealed and then placed into a shaker-like device, which breaks apart the cells, which releases the DNA. The solution with the newly released DNA is mixed with other chemicals and then placed into the qPCR machine, which begins to measure the amount of the particular DNA you are searching for.
“You are able to find your target, and the PCR makes more copies of that target DNA you are trying to find,” explains Dr. Noble, gesturing to the PCR, which looks like a series of black computer hard drives linked together. “So it’s a series of chemical reactions, and a series of heating and cooling cycles, and by the time you get to the end of the process, you are able to quantify the target, or you find there was nothing.”
Think of the qPCR as a biological super printer. The continual heating and cooling cycle speeds up the copying of DNA, which allows for a quicker analysis.
The researcher measures the concentration in the target DNA and compares it to a series of known standards. From that, the concentration of the DNA in the water is determined. The quicker the qPCR test indicates that there is a potentially dangerous amount of indicator bacteria from the beach water sample, the faster there's an indication the beach should be closed.
The test is not only quicker. It is also accurate. The EPA has studied the test and the results it provides and has approved its use for testing beach water.
Orange County, California is using the rapid water test for Enterococcus and posting results at beaches.
The City of Racine, Wisconsin is using the rapid water test for E Coli.
Several agencies in other states as well as the North Carolina Recreational Water Quality Monitoring Section are now evaluating Dr. Noble’s test and comparing it with their current tests.
Dr. Noble, who says she loves the beach, is pleased the time between taking water samples and warning of possible danger has been dramatically reduced.
“We hope to make the time even shorter, that’s our goal,” says Dr. Noble. “We don’t want to make people unnecessarily concerned, about naturally found bacteria that are doing good things in the environment. But we want to know about those that are making people sick."