In coastal areas of the Japan Sea in southern Hokkaido, the isoyake phenomenon (seaweeds such as Laminaria withering on the beach) has been observed over a longperiod of time. The cause of isoyake is attributed to grazing by sea urchins andlack of nutrients and trace elements such as iron in the sea water. A method to prevent grazing by sea urchins while supplying trace elements to promote the growth of seaweed was looked into.
Sea urchins can not move on a sandy bed, so blocks were placed thereon. Ferrous ions to promote photosynthesis were supplied. An experiment on seaweed bed formation was carried out continuously over a period of 5 years.
Seaweed bed formation was successfully achieved, aided by the prevention of sea urchins entering. The standing crop of seaweed benefited from the supply of ferrous ions.
