Mercury methylation in aquatic environments is a key process that incorporates this neurotoxin into the food chain and ultimately the human diet. Mercury methylation is considered to be essentially biotic and mainly driven by sulfate-reducing bacteria present in the bottom sediments in aquatic systems. However, in recent decades, many researchers have shown that this methylation also occurs in oxic layers in conjunction with a high content of particulate organic matter and localized depletion of dissolved oxygen. The goals of this review are to summarize our current understanding of Hg methylation in water columns of both marine and freshwater environments, as well as to highlight knowledge gaps and future research needs. Most of the literature showed that suspended particles (known as marine and lake snow) could be the microenvironment in which Hg methylation could occur across oxic water columns, because they have been recognized as a site of organic matter mineralization and as presenting oxygen gradients around and inside them. To date, the majority of these studies concern marine environments, highlighting the need for more studies in freshwater environments, particularly lacustrine systems. Investigating this new methylmercury production environment is essential for a better understanding of methylmercury incorporation into the trophic chain. In this review, we also propose a model which attempts to highlight the relative importance of a MeHg epilimnetic path over a MeHg benthic-hypolimnetic path, especially in deep lakes. We believe that this model could help to better focus future scientific efforts in limnic environments regarding the MeHg cycle.

在水生环境中，甲基化汞是一个关键过程，它将这种神经毒素整合到食物链中，并最终整合到人类饮食中。汞甲基化被认为是基本上生物的，主要由水生系统底部沉积物中存在的硫酸盐还原细菌所驱动。但是，近几十年来，许多研究人员表明，这种甲基化作用还与高含量的颗粒有机物和溶解氧的局部耗竭一起在含氧层中发生。这篇综述的目的是总结我们目前对海洋和淡水环境中水柱中汞甲基化的理解，并强调知识差距和未来的研究需求。大多数文献表明，悬浮颗粒（被称为海洋和湖泊积雪）可能是微环境，在该环境中，Hg甲基化可能会在有氧水柱上发生，因为它们被认为是有机物矿化的场所，并在周围和周围呈现出氧梯度。在他们里面。迄今为止，这些研究中的大多数都涉及海洋环境，从而强调了在淡水环境（特别是湖相系统）中进行更多研究的必要性。研究这种新的甲基汞生产环境对于更好地了解甲基汞结合到营养链中至关重要。在这篇综述中，我们还提出了一个模型，该模型试图突出MeHg上层路径相对于MeHg底栖-非政治路径的相对重要性，尤其是在深湖中。