Water Quality Monitoring

Water quality monitoring for the 2024 season began on May 20, 2024. Should a Town waterbody fail to achieve an acceptable result, advisories will be posted below via a Town of Barnstable Water Quality Report as well as shared on the MyBarnstable mobile app, via social media, and posted at the waterbody site.


Town of Barnstable Water Quality Reports

July 17, 2024 | UPDATE: Keyes Beach Re-Opened to Swimming

Keyes Beach has been re-opened to swimming as of Wednesday, July 17, 2024 at 5:00PM. The re-opening comes after a water re-test sample collected at Keyes Beach reported appropriate conditions. If you have any questions or would like additional updates, please contact...

Cyanobacteria Monitoring Map

Barnstable County has partnered with the Association to Preserve Cape Cod (APCC), a local non-profit environmental organization, to proactively monitor Cape Cod’s ponds for cyanobacteria and, more specifically, the toxins they sometimes produce. For more specifics regarding the particulars of the monitoring program, please visit APCC’s cyanobacteria monitoring web page.

Understanding the Problem

Cyanobacteria are microscopic bacteria that live in all types of waterbodies. A large growth of these bacteria results in algal blooms. These blooms can pollute the water and may even be toxic to animals and people.

When a dramatic increase in a cyanobacteria population occurs, this is called harmful algal blooms (HABs). This often results in the waterbody turning bright green or blue-green, and forms a surface scum or a discoloration of the water column. CyanoHABs may also form a mat on the bottom sediments, making it more difficult to observe. The surface scums or discolored waters can extend several inches below the water surface, or accumulate near shorelines and in coves as a result of onshore wind activity. They often look like pea soup or spilled, blue or green paint; however, the color can also vary. CyanoHABs can cause dissolved oxygen swings that may result in plant and animal die-off, taste and odor issues, and can cause potential public health issues from the cyanotoxins they may release.

Cyanobacteria on Cape Cod

Typically, cyanobacteria’s potential for overgrowth is kept in check by a balance of several different factors, one of which is nutrient availability. All animals and plants require nutrients to grow and thrive, but if an external force makes nutrients either scarce or overabundant, the balance is disrupted. Here on Cape Cod, human activities – from fertilization to faulty septic systems – have introduced an overabundance of nutrients into the environment, which leads to an ecologically unhealthy condition called eutrophication (the process by which a water body becomes enriched in dissolved nutrients such as phosphates and nitrogen). The greater the nutrient availability, the more fuel for cyanobacteria (and other undesirable plant life) to grow and thrive. Global warming also plays a key role with warmer pond temperatures favoring cyanobacteria. Learn more about cyanobacteria monitoring across Cape Cod through Barnstable County’s efforts.

Protect Yourself and Your Pets

Algae Contact

If you have any contact with water, rinse off immediately.

Do Not Drink

Do not swallow water. Do not use water for cooking. Boiling or filtering will not make it safe.


Keep children away from algae in the water or on the shore.

Stay Out

Stay out of the water until further notice. Do not touch scum in the water or on shore.


Do not let pets go into or drink the water or eat scum.


Do not eat shellfish from this water.


No swimming when blooms are present.


Throw away guts, clean fillets with tap or bottled water before cooking.

Stay Informed

When in doubt, it’s best to keep out! Learn more about cyanobacteria by reviewing related materials and resources from trusted sources such as the Centers for Disease Control,  the United States Environmental Protection Agency and more.