Cyanobacteria Monitoring Program

Currently: Seven Orleans Ponds and Lakes are ‘Acceptable’; One has ‘Potential for Concern.’

*OPC volunteers collecting water samples*

Since 2022, volunteers from OPC have worked with the Association to Preserve Cape Cod (APCC) and its cyanobacteria monitoring program to assess seven Orleans lakes and ponds. Each year that group includes Baker’s Pond, Boland Pond, Cedar Lake, Crystal Lake, Pilgrim Lake and Uncle Harvey’s Pond. The seventh pond varies by year: Twinings Pond was added in 2026. These assessments take place regularly, from May through October.

Our freshwater ponds are “the soul of the Cape.” For some, they are places of peace and contemplation. For others, they are fishing holes, or places to swim, kayak and paddle board.

The onset of a cyanobacteria bloom threatens all these pleasures. It often appears as thick scum that can range in color from bright green or blue-green to mustard-yellow, red or brown; it may also have a foul odor. While not all cyanobacteria are harmful, some produce toxins that can be lethal to fish and to birds and mammals that drink from the affected ponds.

OPC cyanobacteria testing volunteers getting training at Pilgrim Lake

Humans in direct contact with the water may develop rashes or other ailments; wind blowing across the bloom may waft toxins into the air, causing respiratory difficulties.

Cyanobacteria are not a new threat to lakes, but excessive accumulations have been increasing in frequency and duration for several decades. The two primary culprits appear to be excess nutrients in lakes due to runoff from septic systems, fertilizers, and animal waste, and warming due to climate change. Recently in Orleans, cyanobacteria blooms have occurred in May, the summer months, and in early fall.

By tracking ponds throughout the monitoring season, OPC and APCC help to forecast when blooms are forming and document those that have formed, enabling the Town of Orleans to take proactive steps to protect public safety and water quality.

You can follow the latest updates below or on APCC’s interactive map, updated daily.