Shenzhen Key Laboratory of Marine Microbiome Engineering, Institute for Advanced Study, Shenzhen University, Shenzhen 518060, China; Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China.
Shenzhen Key Laboratory of Marine Microbiome Engineering, Institute for Advanced Study, Shenzhen University, Shenzhen 518060, China.
J Hazard Mater. 2022 Jun 15;432:128690. doi: 10.1016/j.jhazmat.2022.128690. Epub 2022 Mar 12.
Mangrove ecosystems serve as an important carbon sink but also could be a hotspot that produces neurotoxic methylmercury (MeHg). Although many studies have focused on mercury (Hg) contamination in this carbon-rich ecosystem, our understanding of the effects and mechanisms of the organic matter (OM) regulation of MeHg production in mangrove sediments is still limited. Here, we examined the effects of Hg contamination and OM enrichment on MeHg production in anoxic mangrove sediments and identified the major microbial guilds attending this process. The mangrove sediments possessed a high potential for producing MeHg, but this was counterbalanced by its rapid degradation. Sulfate-reducing bacteria (SRB) such as Desulfobacterales, Desulfovibrionales, and Syntrophobacterales were the major methylators. OM diagenesis significantly changed the biogeochemical conditions, accelerating MeHg degradation in the sediments. The enhanced MeHg degradation could be attributed to the abundant sulfide produced during OM decomposition, which could potentially inhibit the Hg methylation by immobilization of inorganic Hg, abiotically degrade MeHg, and favor the non-mer-mediated degradation of MeHg by SRB. Our study provides both geochemical and microbial clues that can partly explain the low MeHg levels widely observed in mangrove sediments.
红树林生态系统是一个重要的碳汇，但也可能是产生神经毒性甲基汞（MeHg）的热点。尽管许多研究都集中在这个富碳生态系统中的汞（Hg）污染，但我们对有机物（OM）调节红树林沉积物中 MeHg 生成的影响和机制的理解仍然有限。在这里，我们研究了 Hg 污染和 OM 富集对缺氧红树林沉积物中 MeHg 生成的影响，并确定了参与这一过程的主要微生物类群。红树林沉积物具有产生 MeHg 的高潜力，但这被其快速降解所抵消。硫酸盐还原菌（SRB）如脱硫杆菌目、脱硫弧菌目和互营杆菌目是主要的甲基化菌。OM 成岩作用显著改变了生物地球化学条件，加速了沉积物中 MeHg 的降解。增强的 MeHg 降解可归因于 OM 分解过程中产生的大量硫化物，它可能通过固定无机 Hg 来抑制 Hg 甲基化、非生物降解 MeHg 以及有利于 SRB 介导的非甲基化 MeHg 降解。我们的研究提供了地球化学和微生物学方面的线索，可以部分解释广泛观察到的红树林沉积物中 MeHg 水平较低的现象。
