Damariscotta Lake Water Quality Alert


Update - Fall 2024: Water quality monitoring on Damariscotta Lake has concluded for the 2024 sampling season. Please check back in when we resume next May, and follow Damariscotta Lakewatch on Facebook and Instagram for the latest updates.


Best practices are to avoid dense or scummy areas, avoid inadvertently swallowing lake water, keep pets from drinking lake water or licking fur with scum on it, avoid using lake water for household use and drinking, and shower and wash swimsuits after swimming.

Additional information can be found on the state’s webpage: https://www.maine.gov/dep/water/lakes/cyanobacteria.html. 

Midcoast Conservancy staff are actively patrolling for this threat.  We will continue to keep lake users informed on our social media pages (Damariscotta Lake Watch on Facebook and Instagram) as we work with the Maine DEP and Bigelow Labs to monitor conditions.

For assistance with finding solutions to any of the above issues, please contact Midcoast Conservancy. For any questions please email our Damariscotta Lake Watershed Manager, Patricia, at patricia@midcoastconservancy.org.

When reporting any potential issues, please include where you saw the cyanobacteria and send photos.


 Frequently Asked Questions (FAQ)

What is cyanobacteria?

Cyanobacteria (often called blue-green algae) are aquatic bacteria that photosynthesize and have been around for over 3.5 billion years. When conditions are right their numbers can explode causing what we call a “bloom”. Cyanobacteria blooms can present as paint-like smears in the lake or simply turn the water green. Additionally, cyanobacteria are able to regulate their position in the water column so the density can appear to change throughout the day and be different day to day. 

Is it toxic?

The exact species of cyanobacteria  has not yet been identified and we do not have toxin results yet. However, we are encouraging people to be cautious. Degree of exposure is important, the more contact with the cyanobacteria the more potential for toxicity. This can be because of high density of cyanobacteria or prolonged exposure. Avoid areas of high concentration such as scum lines along the shoreline in windy conditions. Do not allow children to play in those areas, do not ingest this water nor allow your pets to drink this water, and shower after swimming. You should not use your lake intake for drinking water as reverse osmosis and boiling does not remove cyanotoxins. Use bottled water for drinking and take quick showers as cyanotoxins can become aerosolized and cause health problems. .

What caused this problem?

The high air and water temperatures combined with excess nutrients (primarily phosphorus) create ideal conditions for algae and cyanobacteria growth. There are multiple ways phosphorus enters a lake, including erosion, fertilizers, septic systems, agricultural sources, and others.

Signs and symptoms of exposure: nausea, vomiting, diarrhea.

What can I do? 

  • Reduce soil erosion by seeding and mulching bare areas

  • Maintain a ribbon of woody vegetation between your property and the lake

  • Direct water from roofs, driveways and roads to stable vegetated areas

  • Contact Midcoast Conservancy to work with the Youth Conservation Corps to address the above issues

  • Eliminate the use of fertilizer on lakefront property

  • Regularly maintain your septic system (contact your local septic service to have your system maintained)

  • Volunteer in your community. Midcoast Conservancy has opportunities for Invasive Plant Patrol, among others

  • Become a member of Midcoast Conservancy

  • Consider getting your property certified as LakeSmart.

  • DEP’s helpful tips for shorefront property owners.

  • Avoid creating a wake as much as possible in the very narrow South Arm. Erosion is reduced if wakes are generated at least 500 feet from shore.

What is Midcoast Conservancy Doing?

  • We are working with DEP to track the status of the cyanobacteria.

  • We have been collecting water quality data, including phosphorus samples in Great Bay, Muscongous Bay, and South Arm since 1977. We track nutrients levels at the surface, mid depth and at the bottom of the lake to track changes over time.

  • We tackle large scale erosion projects on gravel roads, driveways and shoreline, see the Damariscotta Lake Protection Plan.

  • Donate to support our work to protect and restore Damariscotta Lake - THANK YOU!