Seaweeds are macroscopic algae, which form an important component of the marine living resource. Based on their pigmentation, the seaweeds are broadly grouped into green, brown, red and blue green algae. Sri Lanka has a coast line of approximately 1700 km along which many varieties of marine algae are found. About 340 sea weed species belong to different families have been identified in Sri Lanka by several Scientists (Durairatnam, 1961). Few species belong to the groups of red, brown and green algae are economically important as food and as a source of industrial chemicals such as agar - and alginates.
Several surveys were carried out along the coastal areas of the island on seaweeds with a view to utilizing those of economic importance. These investigations revealed that there were many species of algae in the west coast of Sri Lanka (Figure 1) but very few in the east coast since the coast is made up of long sandy beaches and sheltered bays.
The common genera native to Sri Lanka that could be of economic importance are Gracilaria, Gelidium, Sargassum, Turbinaria, Ulva and Caulerpa. The first two genera are belong to the red algae group and they are important as a source of agar - agar. Sargassum and Turbinaria belong to the brown algae and they are also valuable sources for alginates which will be used mainly in the textile industry. Ulva and Caulerpa are in the group of green algae and they can be directly used as human food since they have high nutritive values.