STUDY OF DIATOM FLORA OF MALWA REGION FROM DIFFERENT WATER SOURCES FOR FORENSIC CONSIDERATION

Abstract

Background: Diatoms (class Bacillariophyceae) are silica-walled microalgae whose frustules resist decomposition and chemical digestion, making them valuable forensic indicators. The diatom test distinguishes ante-mortem drowning in which aspirated diatoms cross the alveolar-capillary barrier and reach systemic organs and bone marrow from post mortem immersion, in which systemic distribution is negligible. Genus- and species-level distribution across water bodies further permits identification of a putative drowning site. Despite the widespread forensic use of diatomology in India, no baseline diatomological data exist for the Malwa region of Madhya Pradesh. Aim: To document diatom diversity in water bodies of the Malwa region and establish a photomicrographic reference database for forensic application in drowning investigations. Methods: Water samples were collected from 11 sites across Ratlam, Sehore, Mandsaur, Ujjain, Badnagar, Indore, Hanumantiya, Sanwer and Undasa districts during the dry season (February-April), covering rivers, lakes, reservoirs, wells and confluent waters. Samples were taken 2–3 cm below the surface in pre-rinsed polyethylene bottles, treated with concentrated HCl and Lugol's iodine, sedimented overnight, and concentrated by three cycles of centrifugation at 3,000 rpm. Slides were examined at 400× under compound microscopy with immersion oil, and taxa identified from valve morphology using standard reference floras. Results: Twelve microalgal taxa across ten genera were identified. Navicula, Caloneis and Nitzschia were widely distributed, consistent with their cosmopolitan occurrence in Indian freshwaters. Several genera showed site-restricted distribution: Fragilaria at Badnagar, Cymbella and Gyrosigma at Sahabkhedi, Coelastrum in the Shivna River (Mandsaur), Cyclotella at Triveni (Ujjain), and Guinardia delicatula - a predominantly marine taxon - in Ratlam surface water. Conclusion: This first systematic diatomological survey of the Malwa region provides a photomicrographic reference library enabling comparison with diatoms recovered from victim tissues or bone marrow, supporting both site-of drowning identification and the ante-mortem/post-mortem distinction. Sampling was limited to a single dry season; year-round sampling, SEM, and DNA barcoding are recommended to extend the database.