They come in a variety of shapes including flat sheets, cylinders, strings of beads, spheres, or hair-like filaments. Green algae are common in the intertidal zones and in shallow water as well as in some freshwater habitats, where light is plentiful. Green Sea Velvet , Codium fragile Caulerpa , Caulerpa filiformis Brown Algae - Phylum Phaeophyta Brown algae have additional pigments which mask the green chlorophyll. These pigments allow the brown algae to extend their range down into deeper waters because the pigments are more efficient than green chlorophyll in absorbing the sunlight down away from the ocean surface. Brown algae also come in a wide variety of forms.
Some brown algae are the largest, longest and most conspicuous seaweeds found on rocky ocean shores.
Some brown algae from southern Australian seas are the fastest growing of all plants. The red colour is not uniform and some species are purple, mauve, orange or even yellow. These pigments allow the red algae to grow at far greater depths than the green and brown algae. Red algae can occur down to 200 metres. Red algae rarely are important in rocky shore or reef communities.