April is a busy transition time for ecologists. Winter data analysis and writing projects need to get wrapped up. Early season field work – such as nesting shorebird and turtle monitoring – gets underway. Planning and preparation for other projects that will be taking place over the coming summer, which once seemed very far away, takes on a sense of urgency. One of the priorities of the Foundation’s Science and Stewardship Department for this upcoming field season will be increased work within the freshwater ponds that many of our properties surround. Thus, we are busy getting geared up for a summer of pond management projects ahead.

A harmful algae bloom (HAB) in progress at Pest House Pond (photo: Karen Beattie).

Pond management is a relatively new endeavor for our organization. It became a heightened priority as a result of recent strategic planning undertaken by our Board of Trustees and staff. According to our most recent plan, adopted in 2019, a component of the Foundation’s foremost strategic objective – continuing careful, thoughtful stewardship of its properties and the mission of the organization – is to “expand stewardship efforts on existing properties to encompass water resources, ponds and shorelands.” Towards that end, we have 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).

Phragmites along the southeastern shoreline of Long Pond (photo: Karen Beattie).

To address these issues, the Foundation has been working with SWCA Environmental Consultants and the Nantucket Land Council (NLC) on our pond management projects. Established in 1981, SWCA is a nationwide company with Massachusetts offices in Boston and Amherst that offers comprehensive environmental planning, regulatory compliance, and natural and cultural resources management services. The Foundation initially contracted with them in 2017 to provide science-based advice regarding the management of one of our smaller ponds (Pest House Pond; see further details below) and has continued to work with them on multiple projects, many of which are being launched this year. The NLC has been involved with island ponds and watershed research since 2009. Below is a description of the sites and management work we will be focusing on during the 2021 field season.

This Google Earth image of Capaum Pond (left) captured a harmful algae bloom in progress (photo: Google Earth).

Capaum Pond (north shore of Nantucket)

Capaum Pond, located along the northwest shore of the island, was once connected to Nantucket Sound and served as the historic harbor for Sherburne (Nantucket’s first town, settled in the mid-1600s). However, the harbor entrance was closed by shifting sands from a storm in 1717; it has been a freshwater pond ever since. Capaum Pond has experienced some serious issues with harmful algae blooms (or HABs) in the past several years. These events and associated water quality trends have been well studied and documented by our colleagues at the NLC.  The Foundation is very grateful to have the NLC as a partner on this and other pond management projects.

A harmful algae bloom (HAB) in progress (photo: Kelly Omand).

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. Although there is little public access to Capaum Pond, addressing the HABs present in the pond is a high priority because of these potential human health risks. The Foundation is a partner in an island-wide HAB monitoring program spearheaded by the Town of Nantucket Natural Resources Department in 2020. This work involves weekly checking and posting of problematic sites to inform and educate the public of risks. Check out a previous blog post by Dr. Jen Karberg about this important work.

SWCA staff conduct assessment work at Capaum Pond in August 2020 (photo: Neil Foley).

The Foundation is currently in the process of applying for permitting with the Nantucket Conservation Commission to address the HAB situation in Capaum Pond with a two-pronged management approach recommended by SWCA: (1) phosphorus inactivation using Alum in the late spring/early summer as an indirect means of preventing algae blooms by precipitating phosphorus in the water column (to remove the algae’s “food source”), and (2) application of copper-based algaecide in late summer/early autumn as a direct means of managing harmful algae blooms that may occur if phosphorus inactivation does not prove completely effective, especially during the first season of treatment. This work will be accompanied by continued, extensive research and monitoring conducted by the NLC. We are also considering a broader watershed assessment to form final conclusions on the source(s) of pond nutrients, particularly phosphorus, and how these sources can be addressed.

Gibbs Pond in the Middle Moors (photo: Danielle O’Dell).

Gibbs Pond (Middle Moors)

This large, deep kettle hole pond in the heart of the Foundation’s Middle Moors properties historically served as a water source for the Milestone Cranberry Bog. Along with Capaum Pond, HABs have been a relatively regular occurrence at Gibbs Pond within recent years. However, unlike Capaum Pond, there are several locations where the public can readily access the pond, which are posted with bilingual educational signage regarding HABs. Moving forward with assessment and management work at this site is therefore a high priority.

The NLC has also done a great deal of monitoring work at Gibbs Pond to document these issues. The Foundation has contracted with SWCA to incorporate this existing data and additional information to be collected over the coming summer to develop a pond management assessment for Gibbs Pond. Once this assessment is completed, we hope to move forward with recommended management options at Gibbs Pond following permitting, hopefully sometime during 2022. Additionally, we have also revised our water management protocols at the Milestone Cranberry Bog to rely solely on well water delivered via an improved irrigation system to address the cranberry operation’s water needs.

Pest House Pond with the pond level control valve installed by the Foundation (photo: Karen Beattie).

Pest House Pond (Shimmo)

This small, ¾ acre pond located in Shimmo adjacent to Nantucket Harbor has experienced HABs for at least the past ten years. Complicating this situation is the existence of a buried outfall pipe (installed in the mid-1900’s prior to Foundation ownership of the pond) that drains the pond directly into the harbor near the beach at the end of Cathcart Road. In order to effectively manage the pond and prevent toxic algae from entering the harbor, the Foundation received permitting in 2017 and installed a valve at the end of the pipe where it enters the pond. The valve remains closed during the summer and early fall, when there are likely to be HABs present. It is occasionally opened during the late fall, winter and spring when water levels are extremely high and in danger of flooding adjacent properties. This management has all but eliminated previously free-flowing inputs from the pond into Nantucket Harbor.

The Pest House Pond outfall pipe flowing into Nantucket Harbor prior to control valve installation (photo: Karen Beattie).

Having the ability to isolate the pond from the harbor has allowed permitted management of excess nutrients and algae to take place using alum and algaecide, similar to what is planned for Capaum Pond. Since SWCA commenced this management in 2018, the presence of HABs has significantly decreased within this shallow water body. Additionally, a small but establishing population of Phragmites along the pond shoreline has been effectively eradicated. Monitoring and additional treatments as needed are planned for this site in 2021.

Tall, dense Phragmites at Hummock Pond (photo: John Krapek).

Long Pond (Madaket) and Hummock Pond (Cisco)

Both of these “Great Ponds” have extensive populations of non-native, invasive Phragmites bordering the majority of their shorelines. Phragmites is one of the most common invasive species on Nantucket and across the entire country. It forms dense, impenetrable monocultures that overtake native wetland species and provides very little beneficial habitat for native wildlife. Furthermore, it is extremely flammable when its tall stems die back after the end of the growing season, posing a wildfire danger.

Phragmites to be treated in 2021 along the southeast shore of Long Pond (photo: Karen Beattie).

In recent years, extensive progress has been made by the Nantucket Pond Coalition managing the Phragmites populations that border Long and Hummock Ponds adjacent to privately owned properties. The Foundation will be working with SWCA this year to initiate management for the portion of the population bordering NCF land along the southeastern shore of Long Pond, having recently been permitted through the Nantucket Conservation Commission for this project. We will be deploying an alternative herbicide (Clearcast by SePRO), which appears to be equally effective to Rodeo, the more commonly used glyphosate-based herbicide that has been the subject of recent controversy as a potential carcinogen. Furthermore, SWCA will be submitting for similar permitting later this spring to treat the western NCF-owned shoreline of Hummock Pond, with management to be initiated this coming fall or in 2022. This invasive species management work at these two sites is being generously supported by pond abutters.

We look forward to providing updates on all of these projects over the coming summer season and in future years. The establishment of extensive invasive species populations and degradation of pond water quality responsible for HABs has occurred over many, many years. It will take much more than a single year of management to successfully get these issues under control.

Capaum Pond (photo: Neil Foley).

The Foundation is extremely grateful for funding recently received by a generous and long-time benefactor to support these types of projects. Two separate funds have been established in memory of a previous Foundation Board of Trustees member by her family: The Lulie Gund Capaum Pond Restoration Fund and the Lulie Gund Nantucket Ponds Restoration Fund. These funds support the analysis, planning, permitting and management actions needed to restore and maintain the health of Capaum Pond and other Nantucket Ponds managed wholly or in part by the Foundation.  Matching support for the Capaum Pond Restoration Fund has been generously committed on a dollar-for-dollar basis up to a total of the first $500,000 raised, and similarly for the Nantucket Ponds Restriction Fund up to a total of the first $1,000,000 raised.

We welcome your support of these efforts! If you would like to contribute a matching gift towards either of these funds, please contact Cormac Collier, the Foundation’s CEO at 508-228-2884 or

Thank you!

The Nantucket Conservation Foundation is a private, non-profit land trust that depends on contributions from our members to support our science projects, conservation property acquisitions and land management efforts. If you are not already a member, please join us now!