Integrated Assessment of Algal Bioaccumulation, Microbial Indicators, and Metal Pollution in a Human-impacted Kuwano River System, Basti (U.P.), India

Aims: This study assessed chemical and microbial contamination in the Kuwano River by (i) quantifying concentrations and spatial distribution of selected heavy metals (Cd, Pb, Zn, Cu, Cr, and trace metals), (ii) evaluating microbial pollution via total coliforms, faecal coliforms, and Escherichia coli, and (iii) determining the Bioaccumulation Factor (BAF). Study Design and Location: An observational field–laboratory investigation was conducted across five stretches (Shivaghat, Atara, Amhat, Mahson, and Lalganj) of the Kuwano River, Basti, Uttar Pradesh, India, during 2025. Methodology: Surface water samples were collected in pre-cleaned HDPE and sterile glass bottles. Heavy metals in water and algal biomass were quantified using Inductively Coupled Plasma–Mass Spectrometry (ICP-MS). Microbial contamination was assessed via membrane filtration to determine CFU/100 mL of total coliforms, faecal coliforms, and E. coli. BAF was calculated to evaluate metal accumulation in algae. Pearson correlation and Canonical Correspondence Analysis were applied to examine relationships between variables. Results: Heavy metal concentrations were higher in algal biomass than in water, indicating significant bioaccumulation. Potassium dominated in water, while Cr, Mn, Fe, and Ni showed spatial variability. High BAF values for Ni, Mn, and Cr confirmed strong accumulation capacity of algae. Cd, Pb, and Cr at some sites approached or exceeded guideline limits. The correlation matrix shows two clusters: microbial indicators and heavy metals. Strong positive correlations among E. coli, faecal coliforms, and total coliforms suggest a common faecal contamination source. Microbial analysis showed elevated total coliforms (585–702 CFU/100 mL), faecal coliforms (292–308 CFU/100 mL), and E. coli (293–398 CFU/100 mL), indicating substantial faecal contamination. Multivariate analysis linked metal distribution to geochemical and anthropogenic factors, and microbial pollution primarily to sewage discharge. Conclusion: The Kuwano River exhibits combined heavy metal and microbial contamination, posing ecological and public health risks. Algae serve as effective biomonitors, while persistent faecal indicators highlight ongoing sewage pollution, necessitating integrated monitoring and improved wastewater management.