Bull kelp is a common name for a number of species of kelp, being the dominant seaweed of exposed rocky coasts around New Zealand and the subantarctic islands. Its thick flexible stipe supports a spongy broad blade or leaf that is usually divided into long narrow straps. A a root-like structure anchors the kelp to the ocean substrate; in this case the exposed rocky coastline is battered constantly by the southern ocean.br/br/Kelp grows in underwater quot;forestsquot; in shallow oceans, and is thought to have appeared in Miocene, 23 to 5 million years ago. They require nutrient-rich water with temperatures between 6 and 14 #176;C and are known for their high growth rate; some species as much as half a metre growth per day to over 80 metres in length.br/br/Bull kelp bags are still used today by South Island Māori to preserve many types of food, and to transport preserved food from one area to another.