Cyanobacterial blooms in lakes continue to make national and regional news headlines. Lake waters are warming, rain events are becoming larger and more intense, and nutrients like phosphorus and nitrogen keep getting added, all of which promote the growth of cyanobacteria. When growth becomes high enough, large accumulations of a single species, or a bloom, can form. Cyanobacterial blooms can be localized and ephemeral, forming near the shore or in a quiescent cove. Blooms can also cover an entire lake and reduce water clarity. In the worst cases, the cyanobacteria produce toxins, which can harm the skin, liver, gastrointestinal tract, or nervous system in humans and pets.
In June of 2024, cyanobacterial blooms resulted in beach closures and health warnings for parts of New Hampshire’s Winnipesaukee and Winnisquam lakes, two large and popular waterbodies about 40 miles west of Sebago. After a couple of weeks, those June blooms dissipated and lake life went back to normal. Unfortunately, they came back for a second round in August and also popped up on Androscoggin Lake, in Leeds, Maine. Unlike in New Hampshire, the Androscoggin Lake cyanobacterial bloom was categorized as a “lake-wide algae bloom” and water clarity plummeted to under five feet.
Closer to home, two nearby lakes had reports of cyanobacterial blooms. Hobbs Pond in Norway had accumulations of a species called Planktothrix in the water. A small surface scum made up of mostly Woronichinia and Dolichospermum species was observed near the shore of Watchic Lake in Standish. LEA took samples from both of these blooms to analyze for the toxin microcystin. While this toxin, which targets the liver, did not show up in the Hobbs Pond sample, the Watchic Lake sample came back positive. Our work on these nearby lakes is part of a statewide effort to document and understand toxic cyanobacteria in Maine.
No cyanobacterial blooms were observed or reported in the LEA service area in 2024. To be clear, the lakes we monitor do contain a variety of cyanobacterial species, some of which can be harmful or toxin-producing. Fortunately, these species rarely accumulate enough to be of concern, though an ephemeral bloom did appear recently on Highland Lake (see the Fall/Winter 2023 Newsletter).
For these reasons, we will continue to monitor the plankton communities in the LEA service-area lakes and keep you informed of any concerning trends. We know some of our members are keen lake observers and notice unusual changes. We encourage you to let us know if you see any green surface accumulations that might mean a cyanobacterial bloom is in progress. And for safety’s sake, please keep yourself, your family, and your pets away from these blooms until they go away.
-Ben Peierls, LEA Research Director
