The three groups of algae are distinguished by types of photosynthetic pigments that is the main difference between green, brown, and red algae. In particular, although algae of the three groups contain chlorophyll a, green algae contain chlorophyll b, brown algae have chlorophyll c, while red algae have chlorophyll d. In addition, red algae contain phycobilins, brown algae have fucoxanthin and xanthophylls, while green algae also may contain xanthophylls. Red and brown algae are mainly marine species, while green algae inhabit mainly freshwater environments. Green algae are commonly unicellular organisms, while red and brown algae are multicellular organisms. As a result, while red and brown algae are sessile, green algae contain flagella and are motile. Finally, brown algae accumulate laminarin, red algae store Floridean starch, while green algae use starch.