Cyanobacteria are the largest, most diverse and widely distributed group of photosynthetic N2 fixing prokaryotes. Cyanobacteria play a vital role in mangrove community food webs. The aerial root system of mangrove trees provides a hard substratum for the attachment of epiphytic algae such as diatoms and cyanobacteria. The paravanar estuary is open type estuary having semidiurnal tides with tidal extending up to a distance of about 10 km. The Poondiyankuppam village is located about 8 km from estuarine mouth. A total of 13 Cyanophycean members were identified. The identified genera were Chroococcus turgidus, Phormidium molle, Merismopedia elegans, Oscillatoria salina, Oscillatoria curviceps, Oscillatoria perornata, Oscill atoria ornate, Oscillatoria minnesotensis, Spirulina subsalsa, Microcoleus acutissimu, Microcoleus chthnoplastes, Nostoc microscopicum, Nostoc carneum. Kadalundi mangrove vegetation provides suitable niche for the growth of phytoplanktons like cyanobacteria. By documenting the cyanobacterial flora of mangrove ecosystems provides a solid foundation for scientific descriptions like ecology to begin the formulation of good management practice.
