Algae are simple, typically small aquatic organisms. They range in structure from unicellular (a single cell that is microscopic) to multicellular and some form colonies that are visible to the naked eye.
Algae can be found attached to various substrates (as periphyton) or free-floating in lakes and rivers (as phytoplankton). Algae form the base of most lake food webs and are valuable and critical components of a healthy aquatic environment. Algae are always present in lakes and rivers.
When conditions are favorable, certain populations of algae can increase to levels that result in poor water quality and an algal bloom or scum may form.
Bloom-forming conditions often include:
Mistaken Identity Algal bloom or something else?
Pollen In the spring and early summer, pollen can collect on the surface of the water in a greenish-yellow hue, looking somewhat similar to blue-green algae. It usually appears dust-like and floats mainly on the surface, but can also form clumps. Over time, the pollen will become waterlogged and sink from sight.
Duckweed There are several small floating plants, such as duckweed, that can make slow-moving water appear bright green. Duckweed is a small (2-5 cm long), disc-like plant with short hair-like roots on the underside. It can form a thick, green blanket on the water surface, looking similar to an algal bloom.