Water Quality


Blue-green algae season is upon us. Here’s how to make sense of it.

After a particularly rainy start to summer, cyanobacteria — commonly referred to as blue-green algae — alerts have already been issued for Owasco Lake and others in central New York. Cyanobacteria are aquatic, photosynthetic bacteria. When we talk about harmful algal blooms, cyanobacteria are our main suspect. Some cyanobacteria produce toxins that are capable of causing harm to humans and animals playing in or drinking the water.

Cyanobacteria are interesting organisms. The earliest cyanobacteria fossils are about 3.5 billion years old, making them one of the oldest organisms on earth. In fact, the oxygen in the air that supports today’s life is largely credited to large populations of cyanobacteria photosynthesizing over millennia to create the high-oxygen-content atmosphere that enables today’s life on earth.

Even though they are not an algae, cyanobacteria are often referred to as blue-green algae for a couple reasons. First, they share several traits with filamentous algae, including appearance and the ability to photosynthesize. (Interestingly, not all cyanobacteria are blue-green: The Red Sea gets its name from occasional blooms of oscillatoria, for instance). Both are unattractive, and when forming thick mats can actually impede water activity such as boating, swimming or fishing. While filamentous algae do not produce toxins, large blooms can still have large impacts on aquatic ecosystems, primarily by causing oxygen depletion.

Some species of cyanobacteria do release cyanotoxins, toxins that can affect the kidneys (hepatoxic), nervous system (neurotoxic) or skin (dermatotoxic). These toxins are a significant safety concern to both humans and pets. The genus microcystis is one of the more common cyanobacteria in our area and is often toxic. When cyanobacteria blooms occur, it is advised to avoid swimming in, drinking or using the water for any purpose. People should also prevent their pets from coming in contact with the water. This goes for any water where you suspect a bloom might be present: discolored water, surface algae or scum, etc.

Cyanobacteria populations in any given water body are influenced by a number of environmental factors; the most prominent include water temperature and supply of nutrients, particularly phosphorous.

Found in Owasco Lake

As part of our educational event on cyanobacteria, Professor Nelson Hairston identified samples of algae brought in by community members. Here are some of the species we found:

Ophrydium versatile – Look like green balls of jelly. They feed on bacteria and small algae and are harmless.

Volvox –A species of green algae.

Merismopedia – The only cyanabacteria found, and only a couple colonies present. It does not bloom. Google to see photos, it is an impressive organism!


CCE is an active partner in the development of watershed action plans and programs that raise awareness of local water quality issues. We provide educational resources for landowners on erosion, plant maintenance, integrated pest management, and more. For news and information about local watersheds take a look at these web sites:

Owasco Lake Watershed

Cayuga Lake Watershed Network

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