Evaluation of bloom dynamics and seasonal abundance of cyanobacteria in eutrophic fish culture ponds at three different regions of Bangladesh

Abstract

Seasonal cycle and bloom dynamics of cyanobacteria in relation to environmental parameters were studied in three areas- Godagari Upazila under Rajshahi district (GD ponds), Bogra city (BG ponds) and Singra upazila under Natore district (SG ponds) from September 2014 to August 2015. Standard methods were followed to analyze the water quality, sediment parameters and cyanobacterial cell density. Except temperature, mean values of all water quality parameters were found significantly different (P < 0.05) among the three study sites. 7 genera of cyanobacteria were identified whereas the highest density was recorded during September in all the studied ponds in order of BG ponds (130.36×10⁶ cells/l) > SG ponds (84.93×10⁶ cells/l) > GD ponds (58.74×10⁶ cells/l). Gradual decrease in cell density was observed from November to January, whereas the lowest density (12.25×10⁶ cells/l) was recorded at BG ponds in December, 2014. Higher values of soil organic matter, total nitrogen and pH were found to play significant role in determining higher cyanobacterial cell density at BG ponds compared to SG and GB ponds. The dominant species recorded in all the three studied regions was Microcystis sp.