Algal Bloom Water Quality Archives

The following content contains archived updates from previous seasons, providing information about bloom conditions on the date listed.

2025 WATER QUALITY UPDATES:

11/13/2025

Secchi Disk Transparency (water clarity) reading of 2.99 meters. Androscoggin Lake is no longer experiencing a lake wide algal bloom (<2 meters). While the clarity has improved from our previous reading, we continue to receive reports of accumulating algal scum along shorelines. Cyanobacteria may release toxins, with the highest concentrations found in scums. These scums should be avoided.

On November 10th, Executive Director Lidie Robbins spoke at Wayne Presents! Androscoggin Lake Algal Bloom forum. She shared updates on the ongoing efforts to understand the blooms and find management solutions. The discussion covered understanding what a bloom is and potential causes, essential data collection, ongoing projects to reduce phosphorus, and the next steps for collaborative management and community action to protect the lake’s water quality. Other speakers included Ted Tucci, ALIC’s President, sharing ways the community can get involved, and Matt Scott, retired DEP lake expert, discussing other lakes that have struggled with algal blooms.

Approximately 150 attended the event (in-person and online). The program was followed by a comments/question-and-answer period. We are working on sharing the answers to these questions and will provide an update when they become available.

Please see below for other updates and information.

10/30/2025

Secchi Disk Transparency (water clarity) reading of 2.24 meters. Androscoggin Lake is no longer experiencing a lake wide algal bloom (<2 meters). While the clarity has improved from our previous reading, we continue to receive reports of accumulating algal scum along shorelines. Cyanobacteria may release toxins, with the highest concentrations found in scums. These scums should be avoided.

Please see below for other updates and information.

10/14/2025

Secchi Disk Transparency (water clarity) reading of 1.69 meters. While the clarity has improved from our previous reading, we continue to receive reports of accumulating algal scum along shorelines. Cyanobacteria may release toxins, with the highest concentrations found in scums. These scums should be avoided.

Please see below for other updates and information.

10/2/2025

Secchi Disk Transparency (water clarity) reading of 1.30 meters. While the clarity has improved from our previous reading, we continue to receive reports of accumulating algal scum along shorelines. Cyanobacteria may release toxins, with the highest concentrations found in scums. These scums should be avoided.

On 9/24/2025, 30 Mile staff accompanied Maine DEP staff to collect additional samples. The results of these collections have concluded the dominant type of algae causing this bloom is a species of cyanobacteria called Dolichospermum. This is the most common bloom-forming species in Maine lakes and is the same species responsible for the blooms in 2021, 2023, and 2024. It is also concluded that there is a detectable amount of microcystin in the lake caused by this species of cyanobacteria, found both at our regular monitoring station and within scum samples collected at the shoreline.

Please see below for other updates and information.

9/18/2025

Secchi Disk Transparency (water clarity) reading of 0.95 meters. We do not recommend swimming in any areas of the lake when the water clarity declines below 1 meter at our regular monitoring location. We continue to receive reports of accumulating algal scum along shorelines. Cyanobacteria may release toxins, with the highest concentrations found in scums. These scums should be avoided.

30 Mile staff has collected algal samples at scum locations in addition to our regular monitoring station for cyanotoxin and taxonomy analysis. Please see below for other updates and information.

9/2/2025

Secchi Disk Transparency (water clarity) reading of 0.96 meters. We do not recommend swimming in any areas of the lake when the water clarity declines below 1 meter at our regular monitoring location. Please see below for other updates and information.

8/19/2025

Secchi Disk Transparency (water clarity) reading of 1.84 meters. Please see below for other updates and information.

8/15/2025

Conditions on Androscoggin Lake have now reached “lake-wide algal bloom” status, with the most recent Secchi Disk Transparency (water clarity) reading taken on 8/15/2025 at just 1.85 meters. The state of Maine defines the threshold for a “lake-wide algal bloom” at 2 meters and a “harmful algal bloom” (or HAB) at 1 meter of water clarity.

The dominant type of algae causing this bloom is not yet confirmed. In 2024, 2023, and 2021, the algae were identified to be a species of cyanobacteria called Dolichospermum. This is the most common bloom-forming species in Maine lakes. Under certain conditions, this type of cyanobacteria can release toxins that are harmful to animals and humans. The reasons cyanobacteria produce toxins is not well understood, and standard monitoring techniques cannot predict when a bloom has toxins in it. Please refer to this Maine DEP webpage for more information and follow these guidelines:

Do not accidentally ingest or drink lake water during a bloom. Well-maintained domestic water treatment systems may make lake water safe to drink by removing bacteria and parasites, but they are not guaranteed to remove algal toxins.
If you shower with lake water, keep showers brief because breathing toxins in shower mist could cause health issues.
Do not swim, water ski, or boat in areas where algae are visible (e.g., pea soup, floating mats, scum layers, etc.), where water is discolored, or where musty odors are present.
Rules of thumb: if you are standing in water chest deep (4-5 feet ) and you can’t see your toes because the water is so green, you should get out; if you are looking into water that is 4-5 feet deep and can’t see the bottom of the lake because the water is so green, you should not to go in.
Because algal scums along the shoreline have the highest concentrations of toxins, do not let children play in water that is discolored, where you see mats of algal material, foam, or where musty odors are present. Do not allow pets or livestock to swim or drink water from these areas.
Rinse off with fresh water and soap if available, as soon as practical if exposed to water that has dense algae present. This will reduce skin exposure for humans and pets.

Please be aware that bloom conditions on your shoreline and throughout the open waters of the lake can change from day to day (or even by the hour) depending on the wind. If water clarity declines below 1 meter at our regular monitoring location, then we do not recommend swimming in any areas of the lake. For the most recent Secchi disk readings, please visit our website: https://30mileriver.org/androscoggin-lake/.

2024 WATER QUALITY UPDATES:

9/12/2024

Secchi Disk Transparency (water clarity) reading of 3.9 meters. Androscoggin Lake is no longer experiencing a lake wide algal bloom (<2 meters).

8/29/2024

Secchi Disk Transparency (water clarity) reading of 1.5 meters. Please read our Frequently Asked Questions (FAQ’s) and see below for other updates and information.

8/15/2024

Secchi Disk Transparency (water clarity) reading of 1.6 meters. Please read our Frequently Asked Questions (FAQ’s) and see below for other updates and information.

08/06/2024

Conditions on Androscoggin Lake have now reached “lake-wide algal bloom” status, with the most recent Secchi Disk Transparency (water clarity) reading taken on 8/5/2024 at just 1.79 meters. The state of Maine defines the threshold for a “lake-wide algal bloom” at 2 meters and a “harmful algal bloom” (or HAB) at 1 meter of water clarity.

The dominant type of algae causing this bloom is a species of cyanobacteria called Dolichospermum. This is the most common bloom-forming species in Maine lakes, and is the same species responsible for the blooms in 2021 and 2023. Under certain conditions, this type of cyanobacteria can release toxins that are harmful to animals and humans. The reasons cyanobacteria produce toxins is not well understood, and standard monitoring techniques cannot predict when a bloom has toxins in it. Please refer to this Maine DEP webpage for more information and follow these guidelines:

Do not accidentally ingest or drink lake water during a bloom. Well-maintained domestic water treatment systems may make lake water safe to drink by removing bacteria and parasites, but they are not guaranteed to remove algal toxins.
If you shower with lake water, keep showers brief because breathing toxins in shower mist could cause health issues.
Do not swim, water ski, or boat in areas where algae are visible (e.g., pea soup, floating mats, scum layers, etc.), where water is discolored, or where musty odors are present.
Rules of thumb: if you are standing in water chest deep (4-5 feet ) and you can’t see your toes because the water is so green, you should get out; if you are looking into water that is 4-5 feet deep and can’t see the bottom of the lake because the water is so green, you should not to go in.
Because algal scums along the shoreline have the highest concentrations of toxins, do not let children play in water that is discolored, where you see mats of algal material, foam, or where musty odors are present. Do not allow pets or livestock to swim or drink water from these areas.
Rinse off with fresh water and soap if available, as soon as practical if exposed to water that has dense algae present. This will reduce skin exposure for humans and pets.