Cyanobacteria and associated environmental factors in Lake Nainital, Uttaranchal, India

Species richness and abundance of cyanobacteria along with associated environmental factors viz., water temperature, secchi disc transparency, pH, dissolved oxygen, free carbondioxide and concentrations of nitrogen, phosphorus, iron and zinc were monitored from August 2003 to July 2005 in Lake Nainital, Uttaranchal India. The lake was a eutrophic and warm monomictic water body undergoing circulation for a period of two months during winters. The concentrations of ammonium, nitrate, phosphate and other nutrients were generally high, and the water was alkaline throughout the study period. Dissolved oxygen remained near saturation except during winter circulation. Cyanobacteria appeared in the lake only from July to December in both years. Microcystis aeruginosa was the only species of the 8 identified cyanobacteria that developed obvious surface blooms in the form of scum. All other species had only small and isolated increases and decreases throughout the study period.