Cyanobacterial diversity of loktak lake, the largest freshwater wetland in north-eastern region of India

Loktak Lake, the largest fresh water lake of North-east India supports a significant population of several species of flora and fauna. In the present study, a survey was conducted to know the cyanobacterial diversity of the lake. A total number of ninety (90) cyanobacterial species belonging to 11 genera were recorded from this wetland. Out of 90 species, 16 were in summer season, 21 in rainy season and 53 in winter season. The number of cyanobacterial strains was more in winter than in summer and rainy seasons. Heterocystous forms showed more frequency of occurrence than non-heterocystous forms. Out of the different habitats, hydrophytes (phumdis) were found to be supporting maximum number of cyanobacterial species whereas waterlogged soil supported the least. Majority of the dominant genera (heterocystous filamentous forms) were observed in winter and summer season. The highest cyanobacterial diversity, Shannon index (H’) was observed for Nostoc (H’=2.16) and the lowest for Limnothrix (H’=0.86). Highest species dominance (Simpson’s index, 1-D) was showed by Nostoc, 0.89 and the lowest found in Limnothrix, 0.5. The diversity of cyanobacteria in the Loktak Lake has not been studied except for a few sporadic reports. The study revealed that the Loktak Lake and its surroundings provide a suitable for diverse groups of cyanobacteria.