Scientists from the newly created Northwest Atlantic Seal Research Consortium (NASRC) are using data collected by the Massachusetts Department of Public Health (MDPH) to investigate whether seals may impact beach water quality along Outer Cape Cod.
A growing population of gray seals has been cited as the reason for beach closures due to poor water quality on the outer Cape. But is there evidence to support these water quality statements?
"We took some basic steps to assess whether there is cause for concern," said Rebecca J. Gast, an associate scientist at the Woods Hole Oceanographic Institution (WHOI) and member of the NASRC. "As far as I know, no one has looked at the data to ask these questions before."
The precise number of gray seals in the area is not known; however, over the last 30 years, in areas where there were once a few hundred, there are now several thousand.
There are three sites or "haul-outs" on the lower Cape where large numbers of gray seals leave the water to avoid predators, regulate their body temperature, and socialize. Sites in the area that host several hundred seals at low tide include High Head on the outer Cape in the National Seashore/Truro area; Jeremy Point on the Cape Cod Bay side of Wellfleet; and North Island in Chatham (see list of beaches).
To conduct their analysis, the researchers examined water quality data from 89 sites at public beaches in six surrounding towns including Provincetown, Truro, Wellfleet, Eastham, Orleans, and Chatham. The water samples, which were collected and analyzed by the MDPH between 2003 and 2012, measure levels of the Fecal Indicator Bacteria (FIB) enterococci, a group of bacterial species which are typically found in human and animal intestines and feces. Although most enterococci do not typically cause illness in humans, it is used to indicate the possible presence of other disease-causing organisms associated with fecal contamination.
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Woods Hole Oceanographic Institution