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Harmful Algal Blooms (HABs) Photo Gallery

The photos on this page provide examples of what a harmful algal bloom (HAB) may look like. For comparison, photos of non-toxic blooms are also provided. It can be hard to tell a HAB from other non-toxic algal blooms and sometimes several types of algae can be present at one time. DEC recommends avoiding contact with any floating mats, scums, or discolored water.

If you see an algal bloom and think it may be a HAB, please submit a Suspicious Algal Bloom Report Form (764 KB). Email the completed form with digital photographs (close-up and landscape to show extent and location) of the suspected bloom to HABsInfo@dec.ny.gov.

Algae is an important part of aquatic ecosystems and forms the basis of lake food chains. There are many types of algae commonly found in the freshwaters of New York. The most common types of HABs are made up of blooms of cyanobacteria (also known as blue-green algae). Individual algae cells cannot be seen with the unaided eye, however, under certain conditions they can cluster together and form visible colonies called blooms.

What do Harmful Algal Blooms (HABs) look like?

HABs on a pond near the shore looks like streaks of green paint on the surface.
HABs may look like parallel streaks, usually green, on the water surface.
HABs look like green dots on the surface of a pond
HABs may look like green dots, clumps or globs
on the water surface. (Photo: Ohio EPA)

Blue-green algae bloom near a rocky pond shore looks like swirls of paint on the water's surface
HABs 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 harmful algal bloom
HABs may make the water look bright green or like pea soup.

What do non-toxic green algal blooms look like?

Green algae can look like floating rafts on the water, 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 like bubbling scum on the water and may be entangled with other plant material, 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 mats at the edge of a pond
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)