Distribution of Nitrogen-Fixing Blue- Green Algae in Various Areas of South and East Asia

Various forms of nitrogen-fixing blue-green algae were isolated from mud samples collected from various districts of southern and eastern Asia. Some of these algae were obtained in bactera-free pure culture (Tolypothrix tenuis, Calothrix brevissima, Anabaenopsis circularis and Nostoc sp.).2. The ubiquitous distribution of nitrogen-fixing blue-green algae throughout tropical, subtropical and temperate regions was discovered. The frequency of their occurrence, however, seemed to be more prominent in the southern than in the northern parts of the areas studied.3. The capacity of 16 species of blue-green algae for assimilating atmospheric nitrogen was determined by chemical analysis.4. The nitrogen-fixing capacity of three representatives of nitrogen-fixers, Tolypothrix tenuis, Calothrix brevissima and Anabaenopsis circularis, was measured with the use of 15N-enriched nitrogen.