Diversity of marine cyanobacteria in island mangroves of Gulf of Mannar Biosphere Reserve, Southeast India

Abstract The present work analysed diversity of cyanobacteria in rhizosphere soil samples, collected from four mangrove species from seven islands of Gulf of Mannar Biosphere Reserve, southeast India. A total of 103 cyanobacterial species belonging to 17 families were identified with 35 unicellular, 21 heterocystous and 47 non-heterocystous forms. The cyanobacterial count was positively correlated with temperature, nitrogen, phosphorus, potassium and total organic carbon, and negatively correlated with salinity and trace metals. The cyanobacterial counts varied with islands and mangrove species and also with environmental parameters, nutrients and heavy metals. Soil salinity was the maximum (48±4.5 ppt) in Shingle Island and the minimum (25±3.1ppt) in Manoli Island but the temperature exhibited a reverse trend. Soil temperature was the lowest (25.1±3.1OC) in Shingle Island and the highest (31.5±4.1OC) in Manoli Island. The Manoli Island exhibited the maximum soil pH (8.8±1.7) and Eh (-131.2±34 mV). The soil pH was minimum in Kurusadai Island (6.7±1.1) while Eh was the lowest in Pullivasal Island (-198.2±41 mV).