Golden-brown in color, diatoms are an unicellular algae. Although tiny, diatoms serve a huge role in the food chain in oceans. They come in a wide variety of shapes. Dinoflagellates are an unicellular, mostly marine algae that are often characterized by their cellulose plates and two perpendicular flagella. Red tide is caused by this group of algae.
Euglenoids are a small phylum of freshwater unicellular algae.
Like the green algae, euglenoids have chloroplasts. A cell wall made of protein makes these algae distinctive. Euglenoids also have two flagella making them mobile . Amoebas can live in freshwater, marine, and terrestrial habitats. Pseudopods, false feet, are one characteristic that distinguishes amoebas from other protozoans.