An update on the seaweed resources of Japan

Natural seaweed beds, which play an important role for coastal ecosystems and marine fisheries, have been changing drastically in Japan. Interventions, such as decreasing the over-grazing by sea urchins, are being undertaken to maintain natural seaweed beds. Japan has at least 15 seaweed genera of economic importance utilized either directly as human food, as ingredients in food, or as raw materials for extraction of chemical compounds for various applications. Most species are produced through various cultivation methods that usually start in a land-based facility and are completed when seaweeds are transferred for open-sea cultivation. Cultivation, as well as harvesting, from natural populations, has sustained the Japanese seaweed industry for many years, but recently a downfall in seaweed production has been experienced in some areas for certain species due to warming oceans. Efforts to improve production have led to the development of forced cultivation techniques to reduce the cultivation period for Saccharina japonica while hybridization of different morphological forms of Undaria pinnatifida has resulted in the production of so-called "southern" and "northern types" that have desirable shapes for harvesting and processing. The future of the seaweed industry in Japan is geared towards producing high-grade products from seaweeds grown in land-based tanks using deep-ocean water.