Cyanobacteria in Brewster Ponds

Cyanobacteria Pond Status

In conjunction with Brewster Ponds Coalition and the Brewster Natural Resources Department the Brewster Health Department is actively monitoring the following ponds for Cyanobacteria. Updates to this table will be made if the risk category of a pond changes.

Acceptable: Pond is deemed safe for recreational activities such as swimming, wading, fishing and boating.

Use Advisory: Avoid contact with the water, do not swallow water, keep pets out and avoid activities such as swimming, fishing, or wading.

Brewster Ponds Coalition Pond Status (Including last sample and/or observation date by the BPC)       The Health Department and Natural Resources Department visit ponds frequently to monitor conditions when notified of a potential bloom. 

What are Cyanobacteria? 

Cyanobacteria have been often referred to as blue-green algae; however, they are a group of microorganisms that share similar characteristics of algae, such as the ability to perform photosynthesis like green plants using the chlorophyll in their cells. Cyanobacteria may occur as single cells, thread-like filaments, or as colonies of various sizes and shapes composed of groups of many filaments or cells. They are naturally occurring in all waterbodies with some species growing in waterbody sediments, while other cyanobacteria can move within the water column. Some cyanobacteria have the ability to produce toxins, called cyanotoxins.

Brewster Ponds Monitoring

In an effort to keep our residents and visitors informed of the current public health advisories for Brewster ponds, we have teamed up with the Brewster Ponds Coalition (BPC) who will report the results by pond to the Health Department and make them available at the BPC website at brewsterponds.org. The Citizen Science Program is testing 19 Brewster ponds for cyanobacteria bi-weekly from May through October.  

When are Public Health Advisories Issued? 

Public health advisory for Harmful Algae Blooms at recreational freshwater locations when at least one of the following criteria is met:

1. A visible cyanobacteria scum or mat is evident; (Most common)
2. Total cell count of cyanobacteria exceeds 70,000 cells/mL;
3. Exceedance of one of the following cyanotoxin guideline values:

• Microcystins - 8 µg/L
• Cylindrospermopsin - 15 µg/L
• Anatoxin-a* – 60 µg/L

Public health advisory for Harmful Algae Blooms are rescinded when there is no visible scum or mat present and the Massachusetts Department of Public Health has completed two successive samples, collected a week apart, demonstrating cell counts and toxin levels below the quantitative guidelines values. 

Public Health Advisories can only be issued by the Brewster Health Department for Brewster's Ponds. 

What should I do if I see a potential CyanoHAB?

The first step an individual should take if they observe a potential CyanoHAB is to AVOID CONTACT with the affected water. While most algae are harmless, cyanobacteria can be skin irritants and some are capable of producing and releasing cyanotoxins, which can make people and animals sick. Contact the Brewster Health Department, and alert them to what you have observed, along with the name and location of the waterbody. 

Additional Cyanobacteria Information:

• MA Department of Public Health Cyanobacteria Information
• Identifying Cyanobacteria Blooms
• MA Department of Public Health Active Advisories
• Barnstable County Cyanobacteria Information
• Brewster Cyanobacteria Poster
• CDC Protect Yourself and Pets
• CDC Cyanobacteria Blooms FAQs