Hydrogeochemical dynamics of acid mine drainage streams and their ecological associations with Bacillariophyceae in the Jaintia Hills, Eastern Himalaya

This study explores the geochemical variables of Acid Mine Drainage (AMD) impacted streams and their influence on Pinnularia biceps , Eunotia exigua , and Pinnularia braunii in the Jaintia Hills of the Eastern Himalayan region. Seasonal water samples were collected from three AMD-impacted streams (AMIS) and one anthropogenic unimpacted stream (AUS) to analyze physicochemical parameters and trace metals following standard protocols. To determine temporal physicochemical variations and assess the associations between geochemical water variables and algal species, multivariate statistical applications, specifically Principal Component Analysis (PCA) and Canonical Correlation Analysis (CCA), were utilized. Results revealed that the concentrations of Fe, Mn, Pb, Zn, Ca 2+ , Cl − , pH, EC, and turbidity varied significantly between AMIS and AUS, with significantly higher levels in AMIS throughout the seasons ( p < 0.05). While these conditions in AMIS pose substantial ecological risks, they support an abundance of some stress-tolerant algae. PCA results indicated that Site I (SI) occupies the lower-stress end, while Site II (SII) represents a transitional state (neither strongly enriched nor pristine). Site III (SIII) depicted the strongest geochemical loading, and Site IV (SIV) showed nutrient and ionic enrichment. Meanwhile, CCA indicated that P. biceps had a positive association with Zn and Fe; E. exigua showed an affinity for Fe, Free CO 2 , EC, and turbidity; and P. braunii exhibited significant associations with EC, DO, and turbidity. These outcomes underscore that, despite the extreme stress conditions of AMD, certain algal taxa serve as effective bioindicators due to their resilient adaptability.