Bone taphonomy and diagenesis contribute to anthropological analysis in forensic investigations by attempting to reconstruct the relationship between human cadaveric remains and their postmortem depositional environment. The rare aquatic taphonomic experiments have been delivering conflicting results on the influence of time and the environment on the decay of bone and teeth, especially considering that the main diagenetic processes can lead to fragmentation, progressive dissolution or fossilization. The aim of this experimental, quantitative, randomized and controlled 2-year study was to analyse the taphonomy and diagenesis of submerged terrestrial mammalian bones to achieve a more accurate estimation of both the post-mortem interval (PMI) and the post-mortem submersion interval (PMSI) in the short term. Three parameters of bone diagenesis, the Oxford Histological Index (OHI), the total porosity and the collagen content of cortical bone were analysed by MicroCT Scan, bright-field Light Microscopy (Picrosirius Red stain), Scanning Electron Microscopy (SEM) and Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) on 75 sheep femurs and tibias placed in four distinct types of environment (natural saltwater, natural freshwater, an artificial seawater solution and exposed to the air) vs. non-exposed controls. LA-ICP-MS was soon discontinued because no measurable changes of the elemental profiles could be detected. Multivariate statistical analysis was applied to the collected data. The macroscopical preservation was consistently excellent (OHI=5). The total porosity and the degradation of collagen were greater underwater than in subaerial exposure, whereas demineralization zones and bioerosion tunnelling appeared after 12 months in the air-exposed samples only. Underwater, the continuous movement, the correlated abrasion by sand and sediment and the constant alkaline pH (≥ 8) can explain the progressive removal of the mineral component and the subsequent exposure of collagen to bioeroders and chemical hydrolysis. On land, the same process occurs at a slower rate on account of the seasonality of the water flow, however, the action of the more abundant and diversified species of bioeroding microorganisms appears more efficient. Despite some limitations, this study indicates that three parameters of bone diagenesis can predict the depositional environment of terrestrial mammalian bone characterized by a PMI and/or PMSI of at least 12 months.

Recent conceptual and empirical developments in decomposition research have highlighted the intricate dynamics within necrobiome communities and the roles of various decay drivers. Yet the interactions between these factors and their regulatory mechanisms remain relatively unexplored. A comprehensive understanding of this facet of decomposition science is important, given its broad applicability across ecological and forensic disciplines, and current lack of research which investigates the inter-dependencies between two critical components of the necrobiome (the microbiome and insect activity), and the consequences of this interdependency on mass loss and total body score. Here we investigated the relationships among these key aspects of the decay process. We experimentally manipulated these variables by physically excluding insects and chemically perturbing the external microbiome of piglet (Sus scrofa) carcasses and quantified the effects on mass loss and total body score, as well as insect pre-appearance interval and colonisation. We found that piglets in the insect excluded and microbially perturbed treatment groups exhibited a significant delay in reaching 50+% of mass loss compared with control piglets with insect access and intact microbiome. However, only remains with insects excluded displayed a significantly slower rate of total mass loss throughout the majority of the experiment and remained a significantly higher mass at the endpoint of 11,000 accumulative degree hours. Additionally, all insect excluded and microbially perturbed treatment groups displayed significantly lower total body scores compared to control piglets at corresponding time points. We also observed a significant delay in insect pre-appearance interval and colonisation for piglets with perturbed microbiomes compared to control piglets. Our findings demonstrate the significance of interacting components of the necrobiome, and the power of manipulative experiments in revealing causal relationships between biota and decomposition rates. These considerations are paramount for developing accurate post-mortem interval estimations and a comprehensive understanding of ecological processes during decomposition.

The succession, development, and behavior of necrophagous insects on decomposing remains are used by forensic entomologists to estimate the minimum post-mortem interval (minPMI). Carcasses are often recovered from concealed environments, such as burials, wrapping, suitcases and waste bins, where they are protected from abiotic and biotic factors, including carrion fauna. The present study represents the first comprehensive research on concealed environments in Australia. Stillborn piglets (Sus scrofa domesticus L.) placed in hard-covered suitcases (N = 40, restricted access) and wheeled bins (N = 20, partially restricted access) were compared with controls (N = 5, exposed) placed on the soil surface, over a period of 164 days (Austral winter to spring). The analysis compared the decomposition process patterns and considered the insect assemblages colonizing the carcasses in each concealment type and the controls. Results show that 1) insects were attracted to the control carcasses within hours of placement in the field (Day 1, D1), followed by wheeled bin carcasses (D3) and suitcase carcasses (D4); 2) carcasses reached skeletonization on D65 (exposed), D108 (wheeled bin) and D136 (suitcase); 3) the assemblages of necrophagous insect species were different between the exposed and the concealed carcasses; 4) blowflies (Diptera: Calliphoridae) were the most prevalent insects colonizing the controls and wheeled bins, while coffin flies (Diptera: Phoridae) were the most prevalent in the suitcases, with some colonized by black soldier flies (Diptera: Stratyiomiidae). The results of this research contribute to the understanding of decomposition processes and insect activity in restricted access environments and help provide a more accurate estimation of the minPMI in forensic cases.