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)
EPA study investigates the tools and techniques used to determine source of fecal contamination at beaches from harbor and gray seals.
Occurrence of recreational water quality monitoring general fecal indicator bacteria and fecal source identification genetic markers in gray seal scat. Paar III, Jack, Jessica R. Willis, Lisa Sette, Stephanie A. Wood, Andrea Bogomolni, Monique Dulac, Mano Sivaganesan, and Orin C. Shanks.Science of The Total Environment 934 (2024): 173220.
The number of gray seals (Halichoerus grypus) observed along the United States Northwest Atlantic region has been increasing for decades. These colonial animals often haul-out on beaches seasonally in numbers ranging from a few individuals to several thousands. While these larger aggregations are an important part of gray seal behavior, there is public concern that haul-outs could lead to large amounts of fecal waste in recreational areas, potentially resulting in beach closures. Yet, data to confirm whether these animals contribute to beach closures is lacking and minimal information is available on the occurrence of key water quality monitoring genetic markers in gray seal scat. This study evaluates the concentration of E. coli (EC23S857), enterococci (Entero1a), and fecal Bacteroidetes (GenBac3) as well as six fecal source identification genetic markers (HF183/BacR287, HumM2, CPQ_056, Rum2Bac, DG3, and GFD) measured by qPCR in 48 wild gray seal scat samples collected from two haul-out areas in Cape Cod (Massachusetts, U.S.A.). Findings indicate that FIB genetic markers are shed in gray seal scat at significantly different concentrations with the Entero1a genetic marker exhibiting the lowest average concentration (− 0.73 log10 estimated mean copies per nanogram of DNA). In addition, systematic testing of scat samples demonstrated that qPCR assays targeting host-associated genetic markers indicative of human,
HIGHLIGHTS
Molecular recreational water fecal diagnostic target occurrence is largely unknown in marine mammal scat.
Three fecal indicator bacteria and six host-associated genetic markers are re- ported in 48 wild gray seal scat samples.
General fecal indicator trends varied by target, while human-, ruminant-, and canine-associated markers were undetectable.
An avian-associated marker was detec- ted in 54.2% of scat samples.
Occurrence information from wildlife is important to interpret recreational water quality results.
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 seal haul-outs and away from seal haul-outs identified in this study.
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.
EPA study investigates the tools and techniques used to determine source of fecal contamination at beaches from harbor and gray seals.
Occurrence of recreational water quality monitoring general fecal indicator bacteria and fecal source identification genetic markers in gray seal scat.
Paar III, Jack, Jessica R. Willis, Lisa Sette, Stephanie A. Wood, Andrea Bogomolni, Monique Dulac, Mano Sivaganesan, and Orin C. Shanks.Science of The Total Environment 934 (2024): 173220.
The number of gray seals (Halichoerus grypus) observed along the United States Northwest Atlantic region has been increasing for decades. These colonial animals often haul-out on beaches seasonally in numbers ranging from a few individuals to several thousands. While these larger aggregations are an important part of gray seal behavior, there is public concern that haul-outs could lead to large amounts of fecal waste in recreational areas, potentially resulting in beach closures. Yet, data to confirm whether these animals contribute to beach closures is lacking and minimal information is available on the occurrence of key water quality monitoring genetic markers in gray seal scat. This study evaluates the concentration of E. coli (EC23S857), enterococci (Entero1a), and fecal Bacteroidetes (GenBac3) as well as six fecal source identification genetic markers (HF183/BacR287, HumM2, CPQ_056, Rum2Bac, DG3, and GFD) measured by qPCR in 48 wild gray seal scat samples collected from two haul-out areas in Cape Cod (Massachusetts, U.S.A.). Findings indicate that FIB genetic markers are shed in gray seal scat at significantly different concentrations with the Entero1a genetic marker exhibiting the lowest average concentration (− 0.73 log10 estimated mean copies per nanogram of DNA). In addition, systematic testing of scat samples demonstrated that qPCR assays targeting host-associated genetic markers indicative of human,
HIGHLIGHTS
Molecular recreational water fecal diagnostic target occurrence is largely unknown in marine mammal scat.
Three fecal indicator bacteria and six host-associated genetic markers are re- ported in 48 wild gray seal scat samples.
General fecal indicator trends varied by target, while human-, ruminant-, and canine-associated markers were undetectable.
An avian-associated marker was detec- ted in 54.2% of scat samples.
Occurrence information from wildlife is important to interpret recreational water quality results.
Findings suggest that using enterococci to monitor recreational waters may underestimate the presence of gray seal scat, suggesting that fecal waste from these animals could play a minor role in local recreational beach closures and advisories.