The Association to Preserve Cape Cod along with volunteers, pond associations, towns and the state monitors over 100 freshwater ponds for concentrations of cyanobacteria (blue green algae) and toxins produced by the bacteria.

These toxins can affect the liver and nerves, and pets have died from drinking water from contaminated ponds on Cape Cod.  

More:Cape Cod Times Cyanobacteria Report: Follow along here for the rest of 2022

When levels are high enough the association staff members will alert the towns. The towns then may post a prohibition on swimming and other activities in the pond until the algal population drops.

The blooms usually occur in the late summer, fueled by warm water or high levels of nutrients from fertilizers, runoff or wastewater seeping through the soil.

In some cases higher concentrations can persist through the fall.

Signs warn of the dangers at Santuit Pond where a bloom of cyanobacteria has closed the pond to swimming from 2021.

Here is a list of ponds currently under alert or watch for cyanobacteria:

Santuit Pond in Mashpee. This is based on a sample from Aug. 24, when the association recommended a use restriction. Use restrictions remain because of the large amount of Dolichospermum cell counts. The genus may produce liver and nerve toxins. Blooms of the genus are usually associated with warm nutrient-rich waters.

Santuit Pond also has high levels of E. coli based on the Barnstable County beach sampling program.

Flume Pond in Falmouth remains with a use restriction recommended after a sample taken Aug. 23. The water temperature is still 76 degrees and microcystin levels remain above 17 parts per billion. 

Long Pond in Barnstable is now on watch as a pond of potential concern. Cyanobacteria was sampled along the shoreline Aug. 29 and remains at acceptable levels, but there is a green color to the pond.

Nearby Shubael Pond is a pond of concern. The water temperature is 78 degrees. There is a scum line of cyanobacteria along the edge of the pond. 

Hinckley Pond in Barnstable is now under a recommended use restriction. A large cyanobacteria bloom was confirmed on Aug. 22. Dolichospermum was the dominant species. There was a large bloom on Aug. 16.

North Pond in Barnstable was flagged for potential concern due a visible scum of cyanobacteria. The last sample was Aug. 15.

The West Reservoir in Harwich remains under restriction after sampling on Aug. 24. Cyanobacteria scum is visible and there is a large bloom. 

There is still an advisory up for Lower Mill Pond in Brewster after a large number of cyanobacteria was detected on Aug. 5. Another sample was taken on Aug. 17, and as of Aug. 24, the APCC was still awaiting a cell count. Dolichospermum was the dominant species.

Cliff Pond in Nickerson State Park has been flagged as a pond of special concern after a sample was taken on Aug. 23. There is an algal bloom along the shore. Previously levels were acceptable. 

Myricks Pond in Brewster is also a pond of special concern. There are floating masses of cyanobacteria. 

There is potential for concern at Lovers Lake in Chatham as there was a scum of cyanobacteria on Aug. 24. Previous levels had been acceptable.

Walkers Pond in Brewster is under a use restriction after sampling on Aug. 30. There is a large cyanobacteria bloom in the pond.