Algae on the Squam Lakes: What You Need to Know

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The summer climate of the lakes supports the growth of various life forms, including algae. During the summer months, especially July and August, it is not uncommon to see large masses of green, filamentous algae in the water as you swim or boat through the lake.

Is Algae Normal in Lakes?

The first and maybe most important thing to note is that this is a completely normal occurrence. As nutrients and sunlight become more readily available in the water, these green algae begin to thrive, simultaneously providing food and shelter for a myriad of other organisms within the lake. These green, cloud-like masses are really just colonies of countless, thin strands of single-celled green algae. They are photosynthetic, meaning they use sunlight to break down carbon dioxide into oxygen and carbohydrates for other organisms within the lake, a very vital process within the water.

The growth rate of algae can be increased by environmental factors such as an early ice out or an excess input of nutrients. Additionally, it is not uncommon to see the location of this algae growth vary from year to year depending on which areas contain the most nutrients (phosphorus in particular) at that point in time. A large congregation of these algae can be irritating to lake-goers, as it may get in the way of recreation such as swimming and boating.

Can Algae be Harmful to Humans and Other Animals?

Although these filamentous green algae are not harmful to humans, there are some types of photosynthetic organisms which can pose potential health threats to humans and other animals. If the amount of nutrients, sunlight, and temperature are just right for these cyanobacteria, to thrive, they can form large blooms and are sometimes capable of producing harmful toxins. A cyanobacteria bloom can be identified by a layer of green or bluish algae over the lake, typically with an unpleasant smell.

Increased temperatures and an increase of nutrients can make cyanobacteria blooms more likely. While the Squam Lakes has not had a history of cyanobacteria blooms, there was a confirmed sighting of a small bloom in December of 2017. Due to the increase possibility of blooms, the Squam Lakes Association is now working to start up a cyanobacteria monitoring program. You can follow this link to read more about cyanobacteria:

If you have questions or suspect a cyanobacteria bloom anywhere on the Squam Lakes, contact SLA Director of Conservation Rebecca Hanson.