Cyanobacteria - 2023 Overview

If its green don not go in (cyanobacteria)Cyanobacteria  is a very serious concern for human and four legged swimmers.  It is present in all of our ponds. With certain environmental conditions, specifically higher temperature and rainfall, cyanobacteria can become dangerous. 


Excellent Overview 

Barnstable County’s Department of Health and the Environment Cyanobacteria Monitoring on Cape Cod webpage has an excellent explanation of the difference between the environmental analyses conducted by the Association to Preserve Cape Cod and the public health approach as described by the Massachusetts Department of Public Health. Cyanobacteria Monitoring on Cape Cod - Barnstable County


Sandwich’s 2023 Management Approach

Sandwich staff recommends that information and outreach regarding Cyanobacteria is the best approach given the complexity of the science and the system. The approach outlined below allows people to make their own informed decisions about whether or not to swim in the water. 

Testing provides only a snapshot in time and does not reveal whether a particular bloom is toxic or not.  When in doubt, stay out.

 When in doubt keep pets out (cyanobacteria)

A Media – Website Alert – Facebook and Instagram communication will be issued later today. Each beach season we issue a general pond health advisory about the presence of Cyanobacteria and posts/alerts as needed throughout the season.  Anyone interested in receiving these notices can sign up through the Notify Me button on the homepage of our website, and follow the Town of Sandwich of Facebook and Instagram feeds.   The Cyanobacteria tab on the Department of Public Health page will be updated in the coming weeks.


The Public Health, Recreation Department and Department of Natural Resources have a coordinated onsite approach to cyanobacteria monitoring and advisories at town beaches Oak Crest Cove Beach at  Peters Pond, Wakeby Pond at the Ryder Conservation Area, and Snake Pond.  This protocol is memorialized in staff training and follows the Department of Public Health’s Guidance on cyanobacteria which establishes the Town Health Director as responsible for issuing advisories.



Each Morning the staff walk the beach and scan the water for physical signs of cyanobacteria. If visible to the staff, even if it isSandwich Cynobacteria Sign not in a swim zone, it is logged in the daily log

Gate attendants are notified.

All patrons visiting the beach are notified that a cyanobacterial bloom was observed. Lifeguards, Recreation and DNR Staff advise patrons when they arrive at the beach.


When cyanobacteria is observed in swim areas, the Recreation Director informs the Health Director.

A physical Advisory Notice is posted. Swimming lessons, or Recreation program swimming is cancelled, patrons are personally informed of the Advisory. The dated Advisory remains posted and is only replaced when a subsequent Advisory is needed.   Each Advisory lists all prior observations for the season.  Many patrons chose to use our waterways after advised.  A copy of the Advisory is attached. 


Improvements Planned for 2023

Kiosks for a public information were funded in the 2023 Capital Plan and have been ordered.  New kiosks will provide a more appropriate site for cyanobacteria and other public information.

General Pond Advisory signs using CDC informational material, similar to the attached will be ordered and installed annually.  Similar to Shark Advisory and Tick Awareness, cyanobacteria is part of the environment and more permanent communication is needed.  A website update is in the works. 


Other Possible Future Considerations & Resources for Future Discussion

The Commonwealth of Massachusetts has treated Cliff Pond in Nickerson State Park with alum as part of its pond health program.  Sandwich has studied this possibility in a 1998 report by Lycott environmental and The Town’s  2018 Twelve Pond Study considers options to improve pond health. 


Testing Approaches and Responses 

1. Massachusetts Department of Public Health 

“Since 2008, MDPH has recommended that individuals be advised not to contact the water when a visible scum or mat is present, the total cyanobacteria cell count exceeds 70,000 cells per milliliter of water (cells/ml), or the microcystin level equals or exceeds 14 parts per billion (ppb). These recommendations are typically made to the local health department, which issues the advisory.”   (bold added for emphasis)


2. Association for the Preservation of Cape Cod

“APCC will collect pond water samples and use a predictive methodology called CyanoCasting. While this method provides useful information regarding cyanobacteria presence and abundance, it does not provide data regarding the existence or quantity of harmful toxins.” (underline and italics added for emphasis)

“APCC will recommend lifting a recreational use advisory or closure after two consecutive tests a week apart show microcystin concentrations less than 8 parts per billion (ppb) and little to no presence of cyanobacteria bloom material, depending on the basis for the original restriction. Health agents are solely responsible for the issuance and removal of recreational use advisories or closures related to water clarity, such as clarity less than 4 feet.”