The main uses of brown seaweeds are as foods and as the raw material for the extraction of the hydrocolloid, alginate. The more useful brown seaweeds grow in cold waters in both the Northern and Southern Hemispheres. They thrive best in waters up to about 20°C. Brown seaweeds are found in warmer waters, but these are less suitable for alginate production and rarely used as food.
Brown seaweeds as food
Food from brown seaweeds comes mostly from the genera Laminaria, Undaria and Hizikia. Originally, harvests of wild seaweeds were the only source, but since the mid-twentieth century demand has gradually outstripped the supply from natural resources and methods for cultivation have been developed. Today, seaweed for food comes mainly from farming rather than natural sources.
Species of the genus Laminaria are eaten in Japan and China, and to a lesser extent in the Republic of Korea. Laminaria was native to Japan and the Republic of Korea, and was introduced accidentally to China, in 1927 at the northern city of Dalian (formerly Dairen), probably by shipping. Prior to that, China had imported its needs from the naturally growing resources in Japan and the Republic of Korea. In the 1950s, China developed a way of cultivating Laminaria on long ropes suspended in the ocean, and this became a widespread source of income for large numbers of coastal families. By 1981, they were producing 1 200 000 wet tonnes annually of seaweed. In the late 1980s, production fell as some farmers switched to the more lucrative but risky farming of shrimp. By the mid-1990s, production had started to rise and the reported harvest in 1999 was 4 500 000 wet tonnes. China is now self-sufficient in Laminaria and has a good export market.
Laminaria was in plentiful supply in Japan, mainly from the northern island of Hokkaido, where several naturally growing species were available. However, as Japan increasingly prospered after the Second World War, demand grew, and by the 1970s cultivation became necessary. They now draw their supply from a mixture of natural and cultivated harvests. In the Republic of Korea, the demand for Laminaria is much lower and most is now provided from cultivation.
Undaria has been harvested from natural resources for many years in the Republic of Korea, China and Japan. The Republic of Korea has the highest consumption of the three countries. Cultivation commenced in the Republic of Korea and Japan in the 1960s, but not until the mid-1980s in China. By 1999, the Republic of Korea was producing about 5 000 wet tonnes of wild seaweed and about 250 000 wet tonnes by cultivation. Some of this was exported to Japan, where production was only 3 000 wet tonnes of wild harvest and 77 000 wet tonnes by cultivation. Laminaria is more popular than Undaria in China, and by the mid-1990s China was harvesting about 100 000 wet tonnes of Undaria from cultivation, small by comparison with the 3 million wet tonnes of Laminaria at that time.
Hizikia is popular in Japan and the Republic of Korea. It has been harvested from natural beds, up to 20 000 wet tonnes in the Republic of Korea in 1984, when cultivation was commenced. Since then cultivation, on the southwest coast of the Republic of Korea, has steadily increased so that by 1994 about 32 000 wet tonnes were farmed and only 6 000 wet tonnes harvested from the wild. A large proportion of the Republic of Korea production is exported to Japan, where there is little activity in cultivation of this species.
These are called alginophytes – needing only one word instead of three to describe the seaweed.
These are nearly all harvested from natural resources. A wide variety of species are used, harvested in both the Northern and Southern Hemispheres. Countries include Argentina, Australia, Canada, Chile, Ireland, Norway, Mexico, South Africa, United Kingdom (Scotland and Northern Ireland) and United States of America. More details of the species harvested are given in a later section, dealing with the alginate industry. Cultivation of brown seaweeds like Laminaria and Undaria go through the sexual reproduction cycle, a time consuming and labour intensive process that is expensive, even in low-labour-cost countries. Cultivated raw material is normally too expensive for alginate production. While much of the Laminaria that is cultivated in China is used for food, when there is surplus production this can be used in the alginate industry, probably provided at a lower price that is subsidized by the high price obtained on the food market.