In recent years, the Foundation has been moving forward with projects that address two very serious threats to our freshwater pond ecosystems: harmful algae blooms (caused by excess nutrients) and invasive plant species (specifically common reed, or Phragmites australis).

Although algae are a normal component of all freshwater ponds, their populations can rapidly increase under conditions where excess nutrients are present. HABs are caused by a particular type of algae: Cyanobacteria (or blue-green algae), which sometimes produce toxins that can be harmful to people and pets by affecting the skin, liver, nervous system, and intestines.

For several years, we have been partnering with the Nantucket Land and Water Council to monitor and manage harmful algae blooms (or HABs) detected in our ponds and develop management strategies at several sites. We have been working with SWCA Environmental Consultants to plan and permit treatments at Gibbs and Capaum Ponds, including alum applications (to control phosphorus which feeds algae growth) and algaecide treatment (to control the algae itself).

Beginning in 2023, we also contracted with SOLitude Lake Management (a nationwide environmental firm) to implement the island’s first liquid alum (or Polyaluminum Chloride) application. Prior to 2023, all alum on the island was applied in granular form. The liquid alum was brought to Nantucket via tanker truck and applied as a water column treatment via boat with a trailing application hose – a more efficient way to administer the alum across the pond. All work was performed consistent with permitting through the Nantucket Conservation Commission.

Results at both ponds treated with PAC showed an initial decrease in phosphorus. However, the fully recommended dose of PAC could not be administered due to limited tanker truck capacity and availability of ferry reservations. Nonetheless, the initial results were promising. We are currently assessing options for applying a higher dose of PAC to these ponds in 2024, with a goal of achieving more prolonged reductions in phosphorus and more effective algae control.

Other pond management projects planned for 2024 include an initial PAC treatment in Hummock Pond (a collaboration with the Town of Nantucket, Nantucket Land Bank and Nantucket Pond Coalition) and continued HAB monitoring and treatment at Pest House Pond in Shimmo.

Non-native, invasive Phragmites management along NCF-owned shorelines of Hummock and Long Ponds will continue, along with new management at West Hummock Pond (aka Clark’s Cove) in partnership with the Nantucket Land Bank. We will also continue our collaborative weekly pond surveys with the Nantucket Land and Water Council, Town of Nantucket, and several additional partners to provide notifications to the public about the current locations of HABs and their potential health impacts to both humans and pets.

The Foundation’s pond management efforts are generously supported by a grant from the Gund Family, in memory of former Trustee member Lulie Gund, along with contributions from abutting property owners and island residents.

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SWCA Sampling, NPF Capaum Pond 1 Resized
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