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By August 5th, conditions on Androscoggin Lake had reached “lake-wide algal bloom” status, with a Secchi Disk Transparency (water clarity) reading of just 1.79 meters at our monitoring station, the deepest spot of the lake. By August 15th, clarity had declined to 1.60 meters. The State of Maine defines the threshold for a “lake-wide algal bloom” as falling to 2 meters of water clarity, and a “harmful algal bloom” (or HAB) at 1 meter.
This is the third out of the past four years that the lake has experienced a lake-wide bloom. This year’s bloom appeared a month earlier than last year.
The dominant type of algae causing these blooms is a species of cyanobacteria called Dolichospermum, 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 recommendations on how to minimize your risk.
What are we doing about it?
In 2022, 30 Mile and ALIC began an intensified water quality monitoring program, collecting data needed to better understand why the lake has bloomed in recent years. At the same time, we are working to reduce sources of phosphorus in the watershed. This has included conducting a watershed survey (2023) to identify erosion sites, developing the Androscoggin Lake Watershed Protection Plan, and now working to remediate sources of erosion. 30 Mile received grant funding to support construction costs associated with improvements to town roads, private roads, and other public and private property – all with the goal of reducing phosphorus.
For updates on the algal bloom, FAQs, and more on what you can do to help, visit our website.
For our most recent Secchi disk readings and other water quality data we collect, visit our website.
Photo: 2021 bloom on Dead River
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