Cyanobacterial harmful algal blooms (CyHABs) are increasingly recognized as a major threat to freshwater ecosystems worldwide due to their ability to produce potent toxins such as microcystins. Among these, Microcystin-LR (MC-LR) is one of the most toxic and frequently detected hepatotoxins, posing serious ecological and public health concerns. The present study investigated the occurrence and spatial distribution of MC-LR in three ecologically important urban lakes of the Kashmir Himalaya—Dal Lake, Nigeen Lake, and Anchar Lake—using enzyme-linked immunosorbent assay (ELISA).
Water samples were collected from multiple sites representing different basins and hydrological zones of each lake. Quantification of MC-LR was performed using a commercial ELISA kit designed for environmental water samples. Standard curves exhibited excellent linearity (R² > 0.99), ensuring reliable toxin quantification. A total of 25 sampling sites from Dal Lake, 12 from Nigeen Lake, and 15 from Anchar Lake were analyzed.
MC-LR was detected at all sampling locations, indicating widespread cyanotoxin contamination across the study lakes. In Dal Lake, MC-LR concentrations ranged from 89.56 to 128.57 µg L⁻¹, with a mean concentration of 109.56 ± 10.58 µg L⁻¹. Nigeen Lake exhibited concentrations between 82.85 and 120.71 µg L⁻¹, with a mean of 107.68 ± 12.20 µg L⁻¹. The highest toxin levels were observed in Anchar Lake, where concentrations ranged from 125.71 to 160.00 µg L⁻¹ and averaged 141.52 ± 10.09 µg L⁻¹. Comparative analysis revealed substantially elevated MC-LR accumulation in Anchar Lake relative to Dal and Nigeen lakes, suggesting more severe eutrophication and cyanobacterial bloom intensity. The consistently high concentrations recorded in all three lakes greatly exceed the World Health Organization guideline value for MC-LR in drinking water, highlighting a significant environmental and public health risk. Evidence of extensive cyanotoxin occurrence in Kashmir Himalayan lakes and underscore the urgent need for long-term monitoring, bloom management strategies, and nutrient reduction measures.