Abstract

Background: Diatom analysis is a significant forensic method for identifying antemortem drowning because it detects siliceous microalgae in internal tissues and ambient materials. While natural bodies of water have been widely researched, manufactured stagnant water tanks, which are widespread in cities, have received less attention. These tanks, which are frequently separated from active water supply systems, provide distinct biofilm-rich microhabitats that may support a wide range of diatom assemblages. Aim: This study looks at the forensic possibilities of such surroundings utilising hydrochloric acid (37%) digestion to isolate diatoms. Method: Microscopic investigation of samples from 48 stagnant water tanks in New Town, Kolkata revealed a wide range of diatom species. Results: Dominant genera included Achnanthidium minutissimum, Cymbella tumida, and Gomphonema sierrianum, with site-specific occurrences of Surirella, Coscinodiscus, and Cymbella auxospore. The existence of both motile and non-motile groups (monoraphids, biraphids, and centric forms) suggests ecological resilience and biofilm-mediated survival. Spatial variation in species distribution was found throughout cardinal zones, indicating microclimatic and structural impacts The acid digestion approach protected frustule integrity while also enabling semiquantitative profiling suited for forensic comparison. The acid digestion approach protected frustule integrity while also enabling semiquantitative profiling suited for forensic comparison. Conclusions: Stagnant water tanks provide biologically diverse and forensically relevant microhabitats for diatom analysis. Their incorporation in forensic methods improves drowning site localisation, particularly in metropolitan areas without natural water bodies. The result encourages further comparative research in isolated areas and suggests AI-assisted D-mapping as a scalable technique for automated diatom identification and geolocation. Standardised sampling and multidisciplinary collaboration are required to operationalise diatom evidence in medico-legal investigations.

• 1.   Armstrong E.J. The Medicolegal Autopsy. In: Water-Related Death Investigation: Practical Methods and Forensic Applications. CRC Press; 2021. pp. 205–50.
• 2.   Ludes B.P., Chambre A., Delabarde T. The diatom test in the field of forensic medicine: a review of a long-standing question. International Journal of Legal Medicine. 2024; 1–9.
• 3.   Girela-Lopez E., Beltran-Aroca C.M., GarcíaMozo H. Diatoms in forensic analysis. In: Modern Trends in Diatom Identification: Fundamentals and Applications. Springer; 2020. pp. 239–56.
• 4.   Yukawa N., Kakizaki E., Kozawa S. Diatom and laboratory tests to support a conclusion of death by drowning. In: Essentials of Autopsy Practice: Innovations, Updates and Advances in Practice. Springer; 2012. pp. 1–36.
• 5.   Saini E., Rohilla P. Forensic diatomological mapping: A data base for diatom profiling to solve drowning cases. International Journal of Current Research and Review. 2020; 12(24): 23–31.
• 6.   Singh R., Kaur R. Diatomological mapping of water bodies–A future perspective. Journal of forensic and legal medicine. 2013; 20(6): 622–5.
• 7.   Fish K.E., Osborn A.M., Boxall J. Characterising and understanding the impact of microbial biofilms and the extracellular polymeric substance (EPS) matrix in drinking water distribution systems. Environmental science: water research & technology. 2016; 2(4): 614–30.
• 8.   Gerbersdorf S., Wieprecht S. Biostabilization of cohesive sediments: revisiting the role of abiotic conditions, physiology and diversity of microbes, polymeric secretion, and biofilm architecture. Geobiology. 2015; 13(1): 68–97.
• 9.   Paterson D.M., Hope J.A. Diatom biofilms: Ecosystem engineering and niche construction. Diatom Gliding Motility. 2021; 135–58.
• 10.   Holden P.A. How do the microhabitats framed by soil structure impact soil bacteria and the processes that they regulate? In: The architecture and biology of soils: life in inner space. CABI Wallingford UK; 2011. pp. 118–48.
• 11.   Ma A., Chen M., Yu Q., Chen L., Huang P., Zhang J. A simple optical microscopy-based diatom classification approach for forensic drowning site inference: A pilot study. International Journal of Legal Medicine. 2025; 1–12.
• 12.   Armstrong E.J., Erskine K.L. Investigation of drowning deaths: a practical review. Academic forensic pathology. 2018; 8(1): 8–43.
• 13.   Prevention P. Prevention of drowning. Pediatrics. 2019; 143(5)
• 14.   Tyr A., Lunetta P., Zilg B., Winskog C., Heldring N. The medico-legal interpretation of diatom findings for the diagnosis of fatal drowning: a systematic review. International Journal of Legal Medicine. 2025; 139(2): 729–46.
• 15.   Vinayak V., Goyal M., Mishra V., Rail A. Diatoms as a great forensic tool in investigation of deaths due to drowning: a case study. Journal of Forensic Medicine and Toxicology. 2010; 27(1): 51–4.
• 16.   Scott K.R., Morgan R.M., Jones V.J., Dudley A., Cameron N., Bull P.A. The value of an empirical approach for the assessment of diatoms as environmental trace evidence in forensic limnology. Archaeological and Environmental Forensic Science. 2017; 1(1): 49–78.
• 17.   Karthick B., Hamilton P.B., Kociolek J.P. An illustrated guide to common diatoms of Peninsular India. Gubbi labs; 2013

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