Pediastrum, a flat colony of green algae.

Green algae, also known as Chlorophyta, is one of the three types of seaweeds. Green algae is a division of the kingdom Protista. This group is one of the most diverse, with about 500 genera and more than 7,000 species. Green algae are located in both bays and estuaires. Most live in freshwater and only about 10% of green algae are marine species.  Many species of green algae are microscopic and they are either unicellular or filamentous. Green algae have the same photosynthetic system as vascular plants, which is dominated by the pigments chlorophyll a and b. These pigments give green algae their beautiful color. This group of algae is a very important component of freshwater and marine ecosystems often forming the base of the food pyramid. Green algae also exhibit a wide variety of life cycles including sexual and asexual reproduction.