Weekly Update on Nantucket Pond Conditions and HAB Status

Sampling for Harmful algal blooms (HABs) has started as of June 1, 2026 and will continue weekly throughout the summer.

Signs will be posted near the water at all tested locations. Please check the signs before swimming, boating, fishing, or letting pets near the water. All ponds tested for HABs have had their status switch to Caution. That includes:

• Gibbs
• Hummock
• Capaum
• Long
• Maxcy
• Miacomet
• Sesachacha
• Stump
• Tom Nevers
• Washing

With warming weather, and increasing water body temperatures, algae is expected to grow in abundance, including Harmful Algae. Most samples from ponds (except for Gibbs and Capaum where samples were unavailable) have had HABs detected. However, the concentrations remain below the thresholds that would trigger advisories or closures. As a result, all ponds remain in a cautionary status and will continue to be monitored closely throughout the season.

Meaning of the signs:

• Green: Water activities are okay. Be careful and avoid drinking the water.
• Yellow: Use caution. Reduce direct contact with water. Boating and kayaking are safer choices.
• Red: Stay out of the water. Do not swim, wade, or touch the water or anything in it.

Keeping pets safe
Pets can get sick from harmful algal blooms. Do not let them swim in or drink the water if yellow or red signs are posted.

Thank you for adhering to these suggestions.