Seaweeds - Marine Algae Phyla

The family index has been divided into three separate sections to cover the three main seaweed phyla. Each phylum has a page containing the links to the species for each family.


Sea Lettuce


Green algae are mostly aquatic organisms of marine or freshwater habitats, although they include certain groups which grow on soil, trees or rocks. There are about 100 species of British seaweeds in this group. Generally they are found on the upper levels of the shore and often associated estuaries and with areas of low salinity.

Family Index




Sea Lettuce Ulva lactuca



Bladder wrack



These are often the most dominant seaweeds on rocky shores found from the upper reaches to the sublittoral areas. They frequently show marked zonation. this group includes the kelps and the familiar wracks.

Family Index




Bladder Wrack Fucus vesiculosus



Pepper dulse


Members of this group are variable in both colour and structure. Generally intolerant of dessication they are usually found in rock pools or under the seaweed canopy in sheltered areas. This group includes encrusted or coralline forms where the thallus is stiffened by calcium carbonate within the cells. There are over 400 species on the British list.

Family Index




Pepper Dulse Osmundea pinnatifida