Morphological characterization of culturable cyanobacteria isolated from selected extreme ecosystems of Sri Lanka

Morphologically diverse cyanobacteria significantly contribute to higher microbial diversity in all Sri Lankan ecosystems. They promote promising, safe and low-cost natural alternative solutions for current global demand including food shortage, poverty, deteriorating health patterns, and environmental degradation. Only a few studies have recorded cyanobacterial diversity in some local extreme ecosystems such as hot water springs but most of them remain unexplored. Therefore, this study was carried out to investigate cyanobacterial abundance and diversity in selected extreme ecosystems of Sri Lanka based on the morphological characterization. Water sampling was carried out in selected salt marshes and salt pans, mangroves, hot water springs, and lagoons. Purified, monocultures were isolated by subsequent plate and liquid culturing in BG 11 and GO (N-free) media. Isolated monocultures were morphologically characterized using microscopic images photographed with IMAGE FOCUS 4.0 software. Among 143 isolates, 18 cyanobacterial genera namely: Leptolyngbya, Oscillatoria, Nodosilinea, Anabaena, Geitlerinema, Gloeocapsa, Microcystis, Nostoc, Synechococcus, Lyngbya, Spirulina, Limnothrix, Pseudanabaena, Wilmottia/ Phormidium, and Fischerella could be identified. Among them, one unidentified genera of Chroococcales, Oscillatoriales, and Nostocales were recorded. Salt marshes and salt pans showed the highest cyanobacterial diversity, Leptolyngbya being the most abundant genus. Pseudanabaena was the most abundant genus recorded in hot water springs. This study provides basic infomation of cyanobacteria diversity and abundance in extreme ecosystems in Sri Lanka for future related research and industrial applications, highlighting the necessity of their conservation.