Aquatic conditions & bacterial communities as drivers of the decomposition of submerged remains

• Published in: Forensic science international 2024-08, Vol.361, p.112072, Article 112072
• Main Authors: Bone, Madison S., Legrand, Thibault P.R.A., Harvey, Michelle L., Wos-Oxley, Melissa L., Oxley, Andrew P.A.
• Format: Article
• Language: English
• Subjects: 16s rRNA; Adaptability; Aquatic environment; Bacteria; Bacterial succession; Biofilms; Biomarkers; Cadavers; Community composition; Composition; Cotton; Decomposition; Dissolved oxygen; Dissolved solids; Environmental conditions; Experimental research; Field investigations; Field tests; Forensic taphonomy; Fresh water; Gene sequencing; Hogs; Human remains; Next-generation sequencing; Nylon; Parameter estimation; Parameter identification; Post-mortem submersion interval (PMSI); rRNA; Salinity; Salinity effects; Seasonal variations; Sequence analysis; Time measurement; Total dissolved solids; Trajectory analysis; Trajectory measurement; Variation; Water; Winter
• ISSN: 0379-0738; 1872-6283; 1872-6283
• DOI: 10.1016/j.forsciint.2024.112072

Aquatic decomposition, as a forensic discipline, has been largely under-investigated as a consequence of the highly complex and influential variability of the water environment. The limitation to the adaptability of scenario specific results justifies the necessity for experimental research to increase our understanding of the aquatic environment and the development of post-mortem submersion interval (PMSI) methods of estimation. This preliminary research aims to address this contextual gap by assessing the variation in the bacterial composition of aquatic biofilms as explained by water parameter measurements over time, associated with clothed and bare decomposing remains. As part of three field investigations, a total of 9 still-born piglets (n = 3, per trial) were used as human analogues and were submerged bare or clothed in either natural cotton or synthetic nylon. Changes in the bacterial community composition of the water surrounding the submerged remains were assessed at 4 discrete time points post submersion (7, 14, 21 and 28 days) by 16 S rRNA gene Next Generation Sequencing analysis and compared to coinciding water parameter measurements (i.e. conductivity, total dissolved solids (TDS), salinity, pH, and dissolved oxygen (DO)). Bacterial diversity was found to change over time and relative to clothing type, where significant variation was observed between synthetic nylon samples and bare/cotton samples. Seasonality was a major driver of bacterial diversity, where substantial variation was found between samples collected in early winter to those collected in mid - late winter. Water parameter measures of pH, salinity and DO were identified to best explain the global bacterial community composition and their corresponding dynamic trajectory patterns overtime. Further investigation into bacterial community dynamics in accordance with varying environmental conditions could potentially lead to the determination of influential extrinsic factors that may drive bacterial activity in aquatic decomposition. Together with the identification of potential bacterial markers that complement the different stages of decomposition, this may provide a future approach to PMSI estimations. •Clothing and clothing type have considerable impact on the global variation of decomposer aquatic bacterial communities.•Environmental variables including salinity, dissolved oxygen and pH drive bacterial assemblages of submerged remains.•Similar trends in Proteobacteria: Bacteroid