Research of diatoms and aquatic bacteria for estimating drowned site of a decomposed cadaver

我们收集了68个淡水，半咸水和海水样品从不同地点周围的两条河流的河口在高潮和低潮。海水在河口上游约2.4（盐度，2.2%）和1.2 km（1.8%）处流动，但表面基本上由淡水组成。每50毫升水中含有69 - 22，200个硅藻，其数量因深度而异，并且在相距仅约1.2公里的地点。硅藻的大小为2.8 - 429 μm（平均16.1-59.2 μm）。大型羽状硅藻居住在淡水地区，大多数在到达海洋之前沉积。潮汐和河流的性质往往改变了在同一河口的沉积物组合。我们还在两具浸泡在河口环境中的尸体的血液样本中检测到大量的生物发光细菌。基于16 S rRNA基因的同源性分析将生物发光菌落鉴定为通常栖息在海水中的费氏弧菌和哈维氏弧菌。这些在浸泡尸体血液中的发现表明吸入了咸水或海水，因为我们以前的研究表明很少有其他海洋细菌侵入并在死后占主导地位。这种简单而快速的细菌学测试有可能作为支持溺水死亡结论的标记。

We collected 68 fresh, brackish and sea water samples from various sites around the estuaries of two rivers at high and low tides. Sea water flowed about 2.4 (salinity, 2.2% at the site) and 1.2 km (1.8%) upstream of the estuaries, but the surface comprised essentially fresh water up to the mouth. Sites contained 69 - 22,200 diatoms/50 ml of water and the numbers varied by depth and at sites separated by only about 1.2 km. Diatoms ranged from 2.8 to 429 (mean range, 16.1-59.2)μm in size. Large pennate diatoms populated fresh water areas, and most sedimented before reaching the sea. Tides and the nature of the river often altered diatomaceous assemblages at the same estuarial sites. Caution is recommended for forensic interpretation of aqueous media to deduce drowning sites.We also detected numerous bioluminescent bacteria in blood samples from two cadavers that had been immersed in estuarine environments. Homologous analysis based on the 16S rRNA gene identified the bioluminescent colonies as Vibrio fischeri and V. harveyi, which normally inhabit seawater. These findings in the blood from immersed bodies suggested brackish or marine water aspiration because our previous study showed that few other marine bacteria invade and predominate post mortem. This simple and rapid bacteriological test has potential as a marker supporting a conclusion of death by drowning.