Forensic diatomology of Pong dam reservoir: Implications for drowning diagnosis and site identification

Determining antemortem drowning in medico-legal casework remains a persistent forensic challenge, particularly in bodies exhibiting advanced putrefactive changes, where conventional morphological indicators are no longer discernible. Forensic diatomology provides a critical microtrace-evidence framework for substantiating drowning and enabling immersion-site attribution through ecological fingerprinting of diatom assemblages. Despite the frequent retrieval of suspected drowning victims from the Pong Dam reservoir hydrologically influenced by the Beas river no comprehensive spatiotemporal diatom baseline exists to support comparative forensic analyses. In this study, high-resolution limnological profiling and detailed morphotaxonomic diatom characterization were undertaken across five sampling stations and six seasonal intervals. A total of 113 taxa were identified using light microscopy and standardized diatom preparation protocols. Canonical Correspondence Analysis (CCA) demonstrated statistically robust relationships between diatom community composition, hydroclimatic seasonality, and key physicochemical drivers. The reservoir exhibited pronounced assemblage homogenization, reflecting dominance by environmentally tolerant euryhaline and eurythermal taxa with high dispersal potential. This investigation provides the first spatially resolved, seasonally stratified diatom reference dataset for Pong Dam, delineating site-specific and season-responsive indicator taxa with demonstrable forensic utility. The dataset significantly strengthens diatomological comparison in drowning cases, particularly when postmortem intervals encompass multiple seasonal transitions. These findings enhance diagnostic reliability in immersion-site reconstruction and reinforce the evidentiary value of diatom microtraces in complex medico-legal drowning determinations.