A platform of calcareous sandstone at low tide on the shore of the Southern Ocean,Victoria Australia. The picture shows a forest of oarweed,Eklonia radiata (syn. Laminaria radiata ),a species of brown alga (Phaeophyta). At centre,and below centre left,are arching stipes that grow from the holdfast,which is the point of attachment to the rocky substrate. The blades ("leaves") of the alga arise from the top of the stipe. The plants can withstand short periods of exposure to the atmosphere,but towards high tide are submerged to depths of around a metre or two. Brown seaweeds are also known as kelps. "Kelp" originally referred to the ash from burning seaweed as part of the process of extracting iodine. Brown seaweeds are also a source of mannitol,and alginic acids used in the dressing of fabrics,binders in paper manufacture,and the production of artificial leather |