Chen Xiaoxin, Zhou Yanwu, Mai Zhimao, Cheng Hao, Wang Xun
College of Marine Sciences, South China Agricultural University, Guangzhou 510642, China.
State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China.
Sci Total Environ. 2025 Jan 25;962:178457. doi: 10.1016/j.scitotenv.2025.178457. Epub 2025 Jan 11.
Mangrove ecosystem has attracted global attention as a hotspot for mercury (Hg) methylation. Although numerous biotic and abiotic parameters have been reported to influence methylmercury (MeHg) production in sediments, the key factors determining the elevated MeHg levels in mangrove wetlands have not been well addressed. In this study, Hg levels in the sediments from different habitats (mudflats, mangrove fringe, and mangrove interior) in the Futian mangrove wetland were investigated, aiming to characterize the predominant factors affecting the MeHg production and distinguish the key microbial taxa responsible for Hg methylation. MeHg concentrations in the sediments from the mangrove interior (1.03 ± 0.34 ng g dw) were significantly higher than those in mudflats (0.26 ± 0.08 ng g dw) and mangrove fringe (0.45 ± 0.10 ng g dw). Mangrove vegetation also promoted the accumulation of organic matters in sediments, which stimulated the growth of methylators, ultimately leading to an elevated MeHg level in the sediment. The data from 16S sequencing and random forest analysis further indicated that the increased abundances of Desulfococcus and Desulfosarcina, which belong to complete-oxidizing microbes with acetyl-CoA pathway and are favored by mangrove vegetation, were the primary contributors to MeHg production. Besides, syntrophic partners of methylators (e.g. Syntrophus) also play a considerable role in MeHg production. The present findings provide a deep understanding of Hg-methylation in mangrove wetlands, and offers valuable insights into of the interactions between mangrove plants and soil microbiome in the presence of Hg contamination.
红树林生态系统作为汞（Hg）甲基化的热点地区已引起全球关注。尽管已有大量生物和非生物参数被报道会影响沉积物中甲基汞（MeHg）的产生，但决定红树林湿地中MeHg水平升高的关键因素尚未得到很好的解决。在本研究中，对福田红树林湿地不同栖息地（泥滩、红树林边缘和红树林内部）沉积物中的汞含量进行了调查，旨在确定影响MeHg产生的主要因素，并区分负责汞甲基化的关键微生物类群。红树林内部沉积物中的MeHg浓度（1.03±0.34 ng g干重）显著高于泥滩（0.26±0.08 ng g干重）和红树林边缘（0.45±0.10 ng g干重）。红树林植被还促进了沉积物中有机物的积累，刺激了甲基化菌的生长，最终导致沉积物中MeHg水平升高。16S测序和随机森林分析的数据进一步表明，属于具有乙酰辅酶A途径的完全氧化微生物且受红树林植被青睐的脱硫球菌属和脱硫八叠球菌属丰度增加是MeHg产生的主要贡献者。此外，甲基化菌的互营伙伴（如互营杆菌属）在MeHg产生中也起着相当重要的作用。本研究结果为深入了解红树林湿地中的汞甲基化提供了依据，并为汞污染条件下红树林植物与土壤微生物群落之间的相互作用提供了有价值的见解。
