Pond Monitoring Results

Long Pond Monitoring
If you see scum on the shoreline, please take a photo and send to [email protected]

8/28/26: A significant bloom can be seen at the far north end of the pond, and a lesser bloom on the western side.

APCC 2026 Monitoring Results

.The Association to Preserve Cape Cod takes shoreline samples at the north and south ends of Long Pond every 2 weeks and at the Association Beach monthly.

Subtidal 2026 Monitoring Results

Subtidal’s buoy, located over the deepest part of the pond, provides 24/7 monitoring.

As of 9/2/26, Subtidal reports a significant bloom, and advises avoiding contact with the water. Boating with minimal splash may be acceptable, but avoid kayaking or activities close to the water surface.Phycocyanin levels at the bottom of the pond (a measure of cyanobacteria) have exceeded the levels during our early July bloom.

The above chart is based on data from APCC's monitoring of Long Pond. While there is no threshold level of bloom-forming cyanobacteria that is considered "dangerous", levels around 1,000 micrograms often lead to a harmful algal bloom, which can pose a health hazard for 2 subsequent weeks.

LAST YEAR'S DATA:

The problem with Long Pond is not new.
A 2008 study conducted by the U Mass Dartmouth School of Marine Science and Technology for
the Town of Barnstable revealed that, while not one of the most impaired ponds in town,
Long Pond Marstons Mills was considered unhealthy as many as 15 years ago.
This is evident in the high phosphorus concentrations and low Secchi (water clarity) depths shown in the two graphs below.

The above graph shows average total phosphorus concentrations between June and September 2008 for Barnstable ponds that have depths between 2.1 and 8.6 meters. Pond names have the depths in meters at which readings were collected (e.g., “Eagle0.5 m” is Eagle Pond readings collected at 0.5 m).
The red line is the Cape Cod threshold for healthy pond ecosystems (10 micrograms per liter of TP from Eichner, et al., 2003); bars for ponds with an average TP concentration less than 10 µg/l are colored light blue.

In the graph below, ponds with red bars have average Secchi depths that are less than the state safe swimming clarity limit of four feet, while ponds with yellow bars have shallowest recorded readings that are less than the four-foot limit.