Chapter 12 - Dynamics of cyanobacteria in two thermal water bodies of the Western Ghats

Abstract

Diverse cyanobacteria occurring in several aquatic habitats including the thermal water bodies are influenced by biotic and abiotic factors. Cyanobacteria in thermal spring as well as thermal water discharge channel in the foothill of the Western Ghats have been evaluated. Among 43 species (23 genera in 14 families), the community structure differed between the sampling stations with dominance of nonheterocystous filamentous forms (39.5%) followed by almost equal proportions of unicellular and heterocystous forms (30.2%–30.3%). Seven species were dominant in thermal spring (Oscillatoria annae, O. wellie, Phormidium autumnale, P. orientale, Scytonema bohnerii, S. coactile, and Synnechocystis aquatilis), while only three species in thermal channel (Oscillatoria annae, O. limosa, and O. wellie). Shannon diversity of cyanobacteria was extremely higher in both thermal bodies than the Simpson diversity. Free carbon dioxide, phosphate, and sulfate showed positive correlation with species richness, while total hardness as well as sulfide showed negative correlation in thermal spring. In thermal channel, only DO showed positive correlation, while other nine constituents (free carbon dioxide, total alkalinity, TDS, conductivity, nitrate, sulfate, DO, DOM, and BOD) were negatively correlated with species richness. Thus, there were a fewer controlling factors in the thermal spring compared to the thermal channel, which influenced the cyanobacterial richness, diversity, and dynamics. Cosmopolitan, core-group, and exclusive species of cyanobacteria with influence of physicochemical factors in thermal water bodies have been discussed.