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Savery Pond forms the headwaters of a creek informally known as Herring Brook, one of two fresh surface-water inputs to the Ellisville Marsh Estuary.  It has an area of approximately 30 acres, average and maximum depths of 7 and 12.5 feet (respectively), and is currently undergoing classification as a “Great Pond” by the State of Massachusetts. The pond is spring-fed by local groundwater, with surrounding land uses including residential, forest, cranberry bogs and a commercial campground (primarily used by RVs). People use the pond for fishing, recreation and agricultural water supply; however, Savery Pond provides key ecological functions and plays a significant role in the ecology of Ellisville Marsh.

Map of Savery Pond


Viewing an osprey hunting its fish prey from above, or a turtle sunning on the shore, smelling the clean plant-sweetened air near the pond edge, swimming in pond’s waters or catching its fish are experiences we hope to continue here on Savery Pond. However, inflows and accumulation of nutrients (phosphorus and nitrogen) have caused harmful algal blooms that impact both recreational uses and ecological functions. Specifically:

  •    Summer blooms of blue-green algae have led the MA Dept. of Health and Human Services to issue cyanobacteria advisories on Savery Pond in 2011, 2014 and 2015; and algal blooms have also been noted in other years. Cyanobacteria blooms contain toxins or other noxious chemicals that can pose harmful health risks. People or animals may develop skin irritation or upper respiratory problems from exposure to the blooms, and drinking associated pond water can cause kidney damage, liver damage and gastrointestinal symptoms (in extreme cases, dogs and other animals have even died after drinking pond water containing these toxins).

  •    Decaying organic matter due to algal blooms reduces dissolved oxygen in pond water. This causes a ripple effect throughout the pond ecosystem that can impact fish and other organisms that need oxygen to survive, which in turn affects the birds, reptiles, amphibians, shellfish and mammals that use the pond. Conditions of extreme low dissolved oxygen can lead to fish kills. Periods of low oxygen can also change the minerals present and, over time, the natural chemistry of the pond.

 Reversing harmful algal blooms and reduced dissolved oxygen conditions will require managing the nutrients that cause them. The following information describes what we know about nutrient conditions in Savery Pond, what you can do to help, and the Ecology of Savery Pond. FEM’s goal of improving water quality in the pond will benefit the health of both the pond and Ellisville Marsh Estuary downstream.

Please continue to visit ellisvillemarsh.org > Savery Pond to keep up with the latest developments and information related to our watershed.

What We Know About Nutrients in Savery Pond

Several studies have been performed to characterize excessive nutrient concentrations (eutrophication) in Savery Pond. Phosphorus is typically the controlling nutrient for eutrophication in freshwater bodies; however, in some cases, nitrogen can also control algal blooms. Analysis of pond water samples has shown that both phosphorus and nitrogen concentrations are notably high in Savery Pond. Samples of sediment from the bottom of the pond also show high levels of phosphorus.

Based on experience from other ponds that have adjacent cranberry bogs, we know that the current and former bog operations can cause increased nutrients in both the pond water and the sediments beneath the water. Furthermore, we know that septic systems (especially unmaintained or old septic systems) leach nutrients to groundwater, which can then discharge into the pond. Other nutrient sources include road runoff, waterfowl and natural vegetation.

A summary of past and current studies on water quality and nutrients in Savery Pond can be found here. Friends of Ellisville Marsh (FEM) is currently in the process of formulating a monitoring plan that will identify the most critical factors for eutrophication and observed algal blooms. The monitoring plan includes input from stakeholders, researchers/scientists and government agency staff. Data collection is intended to form the basis of a pond nutrient assessment, which will ultimately lead to a nutrient management plan that includes solutions to reduce/eliminate algal blooms and eutrophication.

What You Can Do to Help

As described above, collecting data to characterize the key sources of nutrients and develop a pond nutrient management plan is key to controlling eutrophication and algae blooms.  Performing such studies also provides a basis for obtaining grant funding to support developing solutions to the problem. As a concerned citizen or local resident, you can help in the following ways:

•    Join the Distribution List: Email us at This e-mail address is being protected from spam bots, you need JavaScript enabled to view it to receive email updates about Savery Pond developments and cyanobacteria advisories.

•    Volunteer: FEM could use help to support pond sampling and the monitoring plan.  If you are interested in participating in the sampling or grant writing, contact us at This e-mail address is being protected from spam bots, you need JavaScript enabled to view it .

•    Contribute: FEM requires funding to perform the data collection required to develop a nutrient management plan and associated remedies. We are pursuing a variety of sources: concerned citizens, pond residents, and both private and public grants. Please contribute directly to FEM’s Savery Pond Initiative (and becoming an FEM member) by making your tax-exempt donation.

•    Educate Yourself and Report Concerns: The State of Massachusetts Department of Health and Human Services Algae Information Page reports cyanobacteria advisories and presents useful information to help assess algal issues and guide responses.  Concerns regarding cyanobacteria blooms should be reported to the State Environmental Toxicology Program (please CC emails regarding cyanobacteria to Kim Tower at the Town of Plymouth Department of Marine and Environmental Affairs).

•    Homeowner Best Practices: Reducing the amount of phosphorus entering the pond is the most important step you can take for keeping the pond healthy. Here are five things you can do today to stop the flow of phosphorus, with more details here.
    1.    Practice Pond-Friendly Lawn Care
    2.    Do Not Encourage Waterfowl by Feeding
    3.    Grow a Native Plant Buffer
    4.    Use Phosphate-Free Soaps and Detergents
    5.    Pump Out Your Septic Tank or Cesspool Regularly