Ganga river water quality assessment using combined approaches: physico-chemical parameters and cyanobacterial toxicity detection with special reference to microcystins and molecular characterization of microcystin synthetase (mcy) genes carrying cyanobacteria

• Published in: Environmental science and pollution research international 2022-02, Vol.29 (9), p.13122-13140
• Main Authors: Kesari, Vigya, Kumar, Sanjay, Yadav, Indrajeet, Chatterjee, Antra, Rai, Shweta, Pandey, Shraddha
• Format: Article
• Language: English
• Subjects: Anabaena; Aquatic Pollution; Atmospheric Protection/Air Quality Control/Air Pollution; Bioindicators; Climate change; Coliforms; Cyanobacteria; Cyanobacteria - genetics; Earth and Environmental Science; Ecotoxicology; Environment; Environmental Chemistry; Environmental Health; Environmental science; Equivalence; Eutrophication; Exposure limits; Genes; High performance liquid chromatography; Indicator species; Ligases; Liquid chromatography; Microcystins; Microcystins - analysis; Microcystis; Parameter identification; Phosphoprotein phosphatase; Protein phosphatase; Quality assessment; Quality control; Research Article; Restoration strategies; Rivers; rRNA 16S; Sampling; Sanitation; Spatial analysis; Toxicity; Waste Water Technology; Water analysis; Water Management; Water monitoring; Water Pollution Control; Water Quality; Water quality assessments; Water quality management; Water sampling
• ISSN: 0944-1344; 1614-7499
• DOI: 10.1007/s11356-021-16589-1

Water quality assessment relies mostly on physico-chemical-based characterization; however, eutrophication and climate change advocate the abundance of toxic microcystins (MCs) producing cyanobacteria as emerging bio-indicator. In the present study, a spatial-temporal analysis was carried out at ten sampling sites of Prayagraj and Varanasi during June 2017 and March 2018 to determine the Ganga River water quality using physico-chemical parameters, cyanobacteria diversity, detection of MCs producing strains and MC-LR equivalence. Coliform bacteria, COD, NO 3 -N, and phosphate are the significant contaminated parameters favoring the growth of putative MCs producing cyanobacteria. National Sanitation Foundation WQI (NSFWQI) indicates water quality, either bad or medium category at sampling points. The morphological analysis confirms the occurrence of diverse cyanobacterial genera such as Microcystis , Anabaena , Oscillatoria , and Phormidium . PCR amplification affirmed the presence of toxic microcystin ( mcy ) genes in uncultured cyanobacteria at all the sampling sites. The concentration of MC-LR equivalence in water samples by protein phosphatase 1 inhibition assay (PPIA) and high-performance liquid chromatography (HPLC) methods was observed in the range of 23.4–172 ng/L and 13.2–97.5 ng/L respectively which is lower than the harmful exposure limit by World Health Organization (WHO). Ganga isolate 1 was identified as Microcystis based on partial 16S rDNA sequence and its toxicity was confirmed due to presence of mcy genes and MCs production potential. These findings suggest the presence of MCs producers as new emerging parameter to monitor water quality index and identification up to species level will be valuable for restoration strategies of river Ganga.