Health advisory issued for Seth’s Pond

The town of West Tisbury has issued a health advisory for Seth’s Pond off Lambert’s Cove Road for high readings of bacteria.

The town’s parks and recreation department and health department posted the advisory on Thursday after detecting enterococci, an indicator organism for safety standards in bodies of water.

Enterococci is a waste bacteria, and sources can include wastewater treatment plants, septic systems, stormwater runoff, and animal waste, according to the Environmental Protection Agency. The presence of enterococci can indicate the existence of other disease-causing viruses or bacteria that can sicken swimmers or consumers of fish from that body of water.

Alex Lam, West Tisbury health agent, tests the pond weekly on Mondays then sends out samples to the Wampanoag Environmental Laboratory for analysis. The sample taken last week, which showed 57.6 enterococci colonies per 100 mL, was in acceptable parameters under single sample criteria, where the threshold is 61 colonies. However, as per state standards, the average of the most recent five samples exceeded acceptable parameters. The mean of five consecutive samples within the same bathing season from a freshwater pond can’t exceed 33 enterococci colonies per 100 mL, which is the case for Seth’s Pond. The average— is currently at 64.8 colonies.

Warmer temperatures can be a catalyst for bacterial blooms, which aren’t visible like an algae bloom, Lam said. There’s been an exceedance of minimum standards for enterococci pretty consistently at Seth’s Pond season after season, he added.

The summer — when there’s no flush and flow of the water, combined with elevated temperatures — is an ideal environment for bacteria to replicate, Andrew Jacobs, manager and environmental technician for the tribal lab, said.

The pond will stay under an advisory until samples are within acceptable parameters.