Water Foul
Researchers pinpoint pollution problems on Catalina Island
By Usha Sutliff, USC News Service
It wasn’t a shark. But something lurking in the waters of Avalon Bay on Catalina Island was making swimmers wary and city officials concerned.
To figure out what was polluting the bay of the popular tourist destination in 2001, the city brought in USC College microbiologist Jed Fuhrman and UC Irvine environmental engineer Stanley Grant. Combining genetic testing and bacterial samples, the scientists found both the concentrations and specific sources of pollution, revealing that aging sewer pipes were leaking human waste into the ocean waters along the shore. Bird feces and animal waste, among other contaminants, may also have contributed to the pollution, say the researchers.
“Previously, it was thought that all the contamination probably came from animal sources,” says Fuhrman, the McCulloch-Crosby Chair in Marine Biology. “But our results suggested that some of the contamination came from leaking sewer pipes under the city.”
The leaking pipes in Avalon’s downtown area have since been repaired, and bacteria levels along the shoreline have decreased by more than 50 percent, according to city officials. After the city pipes were fixed, beach closures declined from 31 in 2001 to 15 in 2002.
Traditionally, beaches are tested for fecal indicator bacteria using methods that provide only general information about the sources of pollution. Those methods can’t always distinguish, for example, whether the indicator bacteria are from human or animal sources because all warm-blooded animals—including shorebirds—have them.
Using a method developed by colleagues in Oregon, Fuhrman and Grant used polymerase chain reaction (PCR)—a laboratory technique that amplifies strands of DNA so they are bountiful enough to be tested—to detect a group of bacteria thought to originate only from human waste. They also used a method to detect human enteroviruses—pathogenic viruses that can be transmitted by water and cause a variety of illnesses. Fuhrman says this was the first time, to his knowledge, that the genetic tests have been used in a beach study of this kind.
“Many people are interested in knowing when contamination arises from human waste, as opposed to animal waste, because the risk of exposure is thought to be higher,” says Fuhrman.
“Tests such as these help to distinguish human from animal sources. Also, by showing we can look for viruses as well as bacteria, we expand the numbers of indicators available,” he says.
The tests may prove to be new weapons in the arsenal against beach water pollution. But they are still in the developmental phase.
“Other tests that attempt to get similar answers are also being tried and compared by a variety of labs, and there are trade-offs between the cost and sensitivity of the tests,” Fuhrman says.
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