Microplastic exposure causes organ damage in Puntius sophore

Microplastic pollution is an emerging threat to freshwater ecosystems, yet remains insufficiently monitored in regions where water quality assessment still depends largely on conventional physicochemical parameters. This study investigates microplastic contamination in a freshwater ecosystem in Kallakurichi, Tamil Nadu, and its sub-lethal effects on the sentinel fish Puntius sophore. Surface water and fish specimens were collected from multiple sampling stations and examined for microplastic presence using Fourier Transform Infrared Spectroscopy (FTIR), followed by histopathological evaluation of intestinal, hepatic, and renal tissues and haematological assessment. Although physicochemical parameters were within permissible limits, FTIR confirmed the presence of polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET), predominantly in the form of fibres. Histopathological alterations, including epithelial lifting, vacuolization, necrosis, and inflammatory infiltration, showed a dose-dependent pattern of tissue damage. Haematological changes further indicated stress-related physiological responses. These findings demonstrate that P. sophore functions as a sensitive bioindicator for microplastic exposure and highlight a critical gap in current water quality monitoring frameworks, which fail to detect emerging micropollutants. The study underscores the urgent need to include microplastic indices in freshwater monitoring programs to safeguard aquatic biodiversity and public health.