Euglenoids, dinoflagellates, and usually Diatoms are unicellular while brown algae, red algae and green algae may be multicellular. Photosynthetic pigments are found in all algae like chlrophyll a and yellow or orange carotenoids. Also, almost all algae is aquatic. Also, all algae are eukaryotes and the sex organs are unicellular in all algae.