Green Algae (Chlorophyta)

Green algae patterns on exposed rock at low tide, Gros Morne National Park, Ontario, Canada
Altrendo Nature/ Stockbyte/ Getty Images

Green algae are found as one-celled organisms, multi-celled organisms, or living in large colonies. More than 6,500 species of green algae are classified as Chlorophyta and mostly live in the ocean, while another 5,000 are freshwater and classified separately as Charophyta. Like other algae, all green algae are capable of photosynthesis, but unlike their red and brown counterparts, they are classified in the plant (Plantae) kingdom.

How Do Green Algae Get Their Color?

Green algae have a dark- to light-green coloration that comes from having chlorophyll a and b, which they have in the same amounts as "higher plants." Their overall coloration is determined by the amounts of other pigmentations including beta-carotene (which is yellow) and xanthophylls (which are yellowish or brownish.) Like higher plants, they store their food mainly as starch, with some as fats or oils.

Habitat and Distribution of Green Algae

Green algae are common in areas where light is abundant, such as shallow water and tide pools. They are less common in the ocean than the brown and red algae but can be found in freshwater areas. Rarely, green algae can also be found on land, largely on rocks and trees.


  • Kingdom: Plantae
  • Phylum: Chlorophyta

The classification of green algae has changed. Once all grouped into one class, most freshwater green algae have been separated into the Charophyta classification, while Chlorophyta includes mostly marine but also some freshwater green algae.


Examples of green algae include sea lettuce (Ulva) and dead man's fingers (Codium). 

Natural and Human Uses of Green Algae

Like other algae, green algae serves as an important food source for herbivorous marine life, such as fish, crustaceans, and gastropods like sea snails. Humans use green algae, too, though not usually as food: The pigment beta carotene, found in green algae, is used as a food coloring, and there is ongoing research into green algae's health benefits.

Researchers announced in January 2009 that green algae could play a role in reducing carbon dioxide from the atmosphere. As sea ice melts, iron is introduced to the ocean, and this fuels the growth of algae, which can absorb carbon dioxide and trap it near the ocean floor. With more glaciers melting, this could reduce the ​effects of global warming. However, other factors can reduce this benefit, including when the algae are eaten and the carbon is released back into the environment.​​​​