Water Quality Issues
Scientists from the Northwest Atlantic Seal Research Consortium 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?
The study focused on beaches around three seal “haul-outs” on the lower Cape where large numbers of gray seals leave the water at low tide to avoid predators, regulate their body temperature, and socialize. Sites in the area 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. (NMFS/USFWS Permit No. 932-1905-00/MA-009526)
Water Quality Near Seal Haul-Outs
Researchers divided the beaches in the lower Cape region into those within 5 miles of seal haul-outs, and those more than 5 miles from seal haul-outs. This distance was thought to be a reasonable distance for the dispersion and inactivation of fecal indicator bacteria (FIB) on a daily tidal schedule. Analysis found that the beaches near the haul-outs actually showed a decreasing trend in yearly FIB exceedance events over the last decade, while the beaches away from seal haul-outs showed an increasing trend. (Courtesy Rebecca Gast, Woods Hole Oceanographic Institution)
Cape Cod beaches near large grey seal haul-outs
Water Quality Graph
Beaches listed by year as Beaches near Seal haulout sites, beaches away from seal haulout sites. Beaches away from any seal haulout had more exceedances than those where seals were present in great numbers.
Last updated: June 23, 2021