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A study of Florida Keys canal water samples indicates high levels of bacterial contamination and low levels of dissolved oxygen, according to The Nature Conservancy's Florida Keys Watch program.
The conservation group assessed the levels of bacterial contamination from water samples collected every two weeks at a series of 17 stations located from Key Largo to Boca Chica.
Some 15 percent of the 300 water samples contained levels of enterococcus bacteria that exceed the U.S. Environmental Protection Agency's (EPA) recommended enterococcus maximum level. Following heavy rain, the number of samples that violated the EPA guideline shot to 41 percent.
Enterococcus bacteria are commonly found in the feces of warm-blooded animals such as raccoons, birds and humans.
"Our preliminary findings suggest that bacterial contamination is present in many of the samples we collect," said Brad Rosov, the Conservancy's marine conservation program manager. "The question that still remains to be answered is what is the source of this contamination."
Although further tests of six canal water samples with high levels of enterococcus bacteria were negative for human viruses, Rosov explained that these samples were taken after heavy rain. Samples following rain are thought to contain high bacteria levels due to the Keys' leaky septic tanks or cesspits, Rosov said.
The finding of low levels of dissolved oxygen is a concern because canal systems with high bacterial, viral or nutrient levels often show low levels of dissolved oxygen. Five of the 17 stations tested contained average dissolved oxygen levels below the state standard of 4.0 milligrams per liter, according to the Conservancy.
The organization plans to expand on these early findings and will continue to collect canal water quality data through September 2003.
"It is important to have at least a year's worth of data to determine the whole picture of water quality in the canals," Rosov said.