Inform yourself to make safe choices
What are Harmful Algal Blooms?
Harmful algal blooms (HABs) are the rapid growth of algae or cyanobacteria that can cause harm to people, animals, or the local ecology. Harmful algae or cyanobacteria can look like foam, scum, paint, or mats on the surface of water and can be different colors. These blooms can produce toxins that make people and animals sick. Blooms occur in fresh water, such as lakes and rivers, and salt water, such as oceans or bays (CDC 2021).
Algae and cyanobacteria are simple organisms that live in the water. Algae and cyanobacteria can rapidly grow out of control, or “bloom,” when water is warm, slow-moving, and full of nutrients. Many types of algae do not produce toxins and not all visible algae is harmful. See the galleries below for examples or visit DEC's Harmful Algal Blooms Photo Gallery.
HARMFUL ALGAL BLOOMS CAN LOOK LIKE (FROM DEC habs photo gallery, SUny oneonta biological field station, Village of Cooperstown Watershed supervisory
On Otsego Lake, microcystis colonies often resemble lines of foam.
Credit: Doug Willies 2023
Foam containing microcystin on Otsego Lake.
Credit: Doug Willies 2023
Foam containing microcystin on Otsego Lake.
Credit: Doug Willies 2023
Microcystin foam along Otsego Lake shoreline.
Credit: Doug Willies 2023
Springfield Landing, September 2022
Credit: Holly Waterfield
Bloom conditions at Biological Field Station Thayer Boathouse, September 2022.
Credit: Holly Waterfield
Thayer Boathouse South, September 2022
Credit: Holly Waterfield
Microcystis (harmful algal bloom causing cyanobacteria) surface accumulation
Credit: Holly Waterfield
Springfield Landing swim area, September 2022
Credit: Holly Waterfield
Springfield Landing looking south, September 2022
Credit: Holly Waterfield
Otsego Sailing Club looking south, September 2022
Credit: Holly Waterfield
Even in relatively clear conditions, microcystin can be present. Fairy Springs looking south, September 2022.
Credit: Holly Waterfield
Streaky formations can form in relatively clear water. Swimming area at Three Mile Point, August 2022.
Credit: Holly Waterfield
Grainy formation on Canadarago Lake, August 2022
Credit: Matthew Dombrowski
Clumpy formation on Canadarago Lake, August 2022
Credit: Matthew Dombrowski
Streaky, paintlike formation on Canadarago Lake, August 2018
Credit: Matthew Dombrowski
Streaky, paintlike formation near dock on Canadarago Lake, July 2021
Credit: Matthew Dombrowski
Closer view of formation near dock on Canadarago, July 2021
Credit: Matthew Dombrowski
Streaky, paintlike formation on Canadarago Lake, August 2018
Credit: Matthew Dombrowski
HABs may make the water look bright green or like pea soup. Location not known.
Credit: DEC
HABs may look like blue, green, or white spilled
paint on the water surface. Location not known.
Credit: DEC
HABs may look like parallel streaks, usually green, on the water surface. Location not known.
Credit: DEC
HABs may look like green dots, clumps or globs on the water surface. Location not known.
Credit: DEC
Often mistaken for harmful algal blooms (FROM DEC HABS photo gallery)
Green algae can look like bubbling scum on the water and may be entangled with other plant material, but do not produce harmful toxins.
Green algae can look silky, hairy or like wet fabric on the rocks, plants or water surface, but do not produce harmful toxins.
Green algae can look like floating rafts on the water, but do not produce harmful toxins.
Green algae can look stringy or hairy or like a tumbleweed in the water
or on the lake bottom, but do not produce harmful toxins.
Green algae can form thick mats on the water surface but do not produce
harmful toxins.