Seaweed diversity in Vietnam, with an emphasis on the brown algal genus Sargassum

Vietnam, a country in South-East Asia, is characterized by a coastline nearly 3300 km long. The coast; stretching from Gulf of Tonkin in the North to the gulf of Thailand in the South, has a predominant North-South orientation resulting in a rich and varied coastal environment. The people in Vietnam have traditionally relied on the rich coastal resources, first by harvesting natural populations and more recently by implementing aquaculture practices. Next to fish and shellfish, marine seaweeds (macroalgae) have traditionally been harvested among most of the Vietnamese coast. A survey of the uses of Vietnamese seaweeds results in 82 species which are considered economically valuable (Chapter 1). Many of these seaweeds are used for human consumption, while others have a role in traditional medicine or are used for colloid extraction (e.g. agar, carrageenan) or as feed for animals. Contrary however to neighboring countries such as China, the Philippines and Indonesia where seaweed mariculture has been seriously developed over the last decades, culturing seaweeds remains a largely marginal activity in Vietnam. Reasons as to why seaweed mariculture has not taken off as compared to the neighboring countries are at least partly to be found in the absence of a phycolloid industry in Vietnam. Instead Vietnam exports large amounts of raw seaweeds, harvested from natural populations, at a low price, and then imports the purified phycocolloids at a much higher price. A steadily growing demand for seaweed-derived products results in an increasing pressure on coastal ecosystems which risk overharvesting of natural populations. This risk is especially eminent for the brown algal genus Sargassum of which approximately 50.000 wet tons is harvested every year. Sargassum represents an important ecosystem engineering species of subtidal coastal habitats. The plants can grow easily up to 3-4 m in length and form dense vegetations with a major nursery function for countless juvenile vertebrate and invertebrate species. If plants, the ...