Harmful algal blooms (HABs) generally occur in standing water such as reservoirs, lakes, or ponds. The appearance of HABs varies widely: blooms usually appear in various shades of green or blue – but may also be red, pink, white, gray, or purple. The texture of blooms may resemble spilled paint, green globules, surface scum, foam, floating mats, or grass clippings.
Some blooms may not be visible on the surface of the water at all times because they rise and fall in the water column during the day. HABs may quickly move or disperse depending on temperature, wind, and weather.
In some instances, HABs occur in rivers. These blooms grow as mats on the bottom of the river, attached to cobbles, rocks, or plants. They may also detach and float downstream.
The photos in this gallery were taken of HABs in Utah, but do not include all possible appearances. When in doubt, stay out!