Photo Gallery of Green and Blue-green Algae

Individual cyanobacteria cells and green algae cannot be seen with the unaided eye. However, under certain conditions they can cluster together and form visible colonies called algae blooms.

Not All Blooms Produce Toxins

It can be hard to tell a harmful algae bloom from other algae blooms, and cyanobacteria can be found in blooms with other algae, we recommend avoiding contact with any floating rafts, scums, and discolored water.

What do non-toxic green algae blooms look like?

Green algae can look like floating rafts on the water, but do not produce
harmful toxins.

Green algae can look like bubbling scum on the water and may be entangled with other
plant material, but do not produce harmful toxins. (Photo: Pieter Bridge)

A frog sitting on a rock looking at a pond with green algae mats in the water

Green algae can look silky, hairy or like wet fabric on the rocks, plants or water
surface, but do not produce harmful toxins. (Photo: Pieter Bridge)

Green algae can look stringy or hairy, or look like a tumbleweed in the water on the lake bottom, but so 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.

Three fingers covered with tiny duckweed plants

Although duckweed can cover the water surface, it is not algae, and does not produce
harmful toxins. It is a tiny aquatic plant with a grainy texture and looks like a miniature
lilypad. (Photo: Ohio EPA)

What do toxic blue-green algae blooms look like?

A blue-green algal bloom on a pond near the shore looks like streaks of green paint on the surface.

Blue-green harmful algae blooms may look like parallel streaks, usually green,
on the water surface.

Blue-green algae look like green dots on the surface of a pond

Blue-green harmful algae blooms may look like green dots in the water, or green globs
on the water surface. (Photo: Ohio EPA)

Blue-green algae bllom near a rocky pond shore looks like swirls of paint on the water's surface

Blue-green harmful algae blooms may look like blue, green, or white spilled
paint on the water surface.

Water on the sandy shore is the color of pea soup because of a blue-green algae bloom

Blue-green harmful algae blooms may make the water look like pea soup.