Be on the Lookout for Harmful Algae Blooms this Month

Be on the Lookout for Harmful Algae Blooms this Month

Those of us who enjoy summertime water recreation activities will want to be ever vigilant this month and on the lookout for algae blooms, especially the potentially harmful blue-green algae blooms that can occur in our waters during August. One of the most dangerous is cyanobacteria blooms. Pillo, The Last Green Valley’s water quality monitoring coordinator and watershed conservation project manager for the Eastern Connecticut Conservation District, provided me with information about the dangers of what are called harmful algae blooms (HABs). She suggested I devote my August column to this issue as a public safety concern. Here is some of the information she provided.

  • Cyanobacteria blooms are referred to as harmful algae blooms because under certain conditions, they produce a by-product of their metabolism that may be toxic to mammals. Not all blooms are toxic, but it is advisable to take precautions as though they are.
  • The US Environmental Protection Agency, working with many partners, including Connecticut Department of Energy & Environmental Protection, the US Environmental Protection, and The Last Green Valley water quality monitoring program, are documenting cyanobacteria blooms and collecting samples using trained volunteers to better document where blooms are being reported, how frequent these blooms are happening and whether they are toxic.
  • Hotter summers over a longer period are contributing to these blooms. Nutrients contained in stormwater runoff help to sustain them.
  • Cyanobacteria are similar to bacteria but have the ability make their own food through photosynthesis.

Pillo said more and more lake groups are becoming aware of the potential hazards of cyanobacteria blooms since TLGV hosted a volunteer lake monitoring workshop in May and have been sending her photos of suspected blooms. She encourages people who live on lakes to be aware of how to identify a potential cyanobacteria bloom and the possible dangers for humans and their pets. She also urges lake groups to become active in TLGV’s water quality monitoring program or the TLGV Water Advisory Committee where important information is shared about water quality concerns in The Last Green Valley. “If the water looks like someone spilled green paint on the surface, please avoid those areas. Humans may get a skin rash from toxins that these organisms sometimes produce. Dogs have died from licking the cyanobacteria from a toxic bloom off their fur.” Cyanobacteria typically need to be concentrated to produce enough toxins to cause harm. Scum on one side of the lake doesn’t mean it isn’t safe to swim on the other side.

The CT DEEP website also has information on blue-green algae blooms.

“Cyanobacteria, also known as blue-green algae, occur naturally in lakes and ponds throughout Connecticut. These microscopic organisms often go unnoticed and cause no harm. However, excessive nutrient pollution and climate change are causing water bodies to experience more frequent nuisance cyanobacteria blooms that may produce and release toxins. When cyanobacteria release toxins, people and animals using the water body for recreation can have health effects. It is important to note that not all algal blooms are harmful algae blooms (HABs), however it is not possible to determine the level of toxins in the water without a more detailed evaluation. Out of precaution it is best to avoid direct contact with water experiencing a bloom. When in doubt, stay out!”

In Connecticut, most cyanobacteria blooms occur from mid-summer to early fall. During a bloom the following conditions may be observed on the surface waters:

  • The water may be cloudy or even thick like pea soup.
  • It may look like someone spilled paint on the water.
  • The water will likely be green or brown.
  • There may be a mat of algae or scum floating on the water surface.

Pillo also referred me to an informative website with important information about cyanobacteria and monitoring efforts for tracking and reporting this dangerous algae. CT DEEP also has a webpage devoted to blue-green algae blooms for regional information. It can be found at

As we enjoy the summer season and enjoy our abundance waterways for recreation, please check the surface water before going in the water, as well as before letting your dog enter the water. Knowledge about our natural world, and issues that are affecting our lakes, ponds and rivers is important if we are to keep ourselves and our pets safe.

We live in a beautiful place called The Last Green Valley National Heritage Corridor. I hope you’ll join me to care for it, enjoy it, and pass it on.

Bill Reid is the Chief Ranger of The Last Green Valley National Heritage Corridor. He can be reached at 860-774-3300 or by email at



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