Squam Lake Algae: What You Need to Know

by Olivia Roberts, 2016 Squam Conservation Intern

Photo credit: http://umaine.edu/mitchellcenter/files/2012/06/Field_Guide-4.pdf

As we march through summer and the days become hotter and hotter, many things happen within the lake. Not only do people seem to gravitate towards it more due to the beautiful weather, but this new climate provides a great opportunity for new life to bud within the lake itself. 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.

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, this green algae begins to thrive, simultaneously providing food and shelter for a myriad of other organisms within the lake. The rapid growth of this algae can also be explained by other environmental aspects such as our early ice out this year. Additionally, it is not uncommon to see the locations 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.

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. Although this particular type of algae is not harmful to humans, a large congregation of this algae can be irritating to lake-goers, as it may get in the way of recreation such as swimming and boating.

Although this filamentous green algae is not harmful to humans, there are some types of algae which can pose potential health threats to humans and other animals. If the amount of nutrients, sunlight, and temperature are just right for these blue-green algae, or 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.

If you suspect a cyanobacteria bloom anywhere on the Squam Lakes, it should be reported immediately to DES by calling (603)-271-2457.

Photo credit: http://des.nh.gov/organization/divisions/water/wmb/beaches/cyano_bacteri...

The easiest way to minimize and prevent excessive algae growth (both green algae and cyanobacteria) in your area is to limit the amount of phosphorus that runs off into the water. Phosphorus is a large component of fertilizers, so reducing or completely eliminating the use of fertilizers in your yard is a great start to solving this issue. There are also methods of physically removing the filamentous green algae, such as pulling or raking it out of the water, however this can be difficult due to the sliminess and fragileness of the algae.

If you notice any algae growth on Squam, please report it using this form or by contacting the Squam Lakes Association directly at (603)-968-7336.