Centro de Estudos em Limnologia, Biodiversidade e Etnobiologia do Pantanal, Universidade Estadual de Mato Grosso, Mato Grosso, Brazil.
Sci Total Environ. 2013 Jul 1;456-457:231-8. doi: 10.1016/j.scitotenv.2013.03.022. Epub 2013 Apr 18.
The toxic potential of mercury (Hg) in aquatic systems is due to the presence and production of methylmercury (MeHg). Recent studies in tropical floodplain environments showed that periphyton associated with the roots of aquatic macrophytes produce MeHg. Periphyton communities are the first link in the food chain and one of the main MeHg sources in aquatic environments. The aim of this work was to test the hypotheses that the algal community structure affects potential methylation, and ecologically distinct communities with different algal and bacterial densities directly affect the formation of MeHg in the roots of macrophytes. To evaluate these, net MeHg production in the roots of Eichhornia crassipes in relation to the taxonomic structure of associated periphytic algae was evaluated. Macrophyte root samples were collected in the dry and flood season from two floodplain lakes in the Pantanal (Brazil). These lakes have different ecological conditions as a function of their lateral hydrological connectivity with the Paraguay River that is different during times of drought. Results indicated that MeHg production was higher in the flood season than in the dry season. MeHg production rates were higher in the disconnected lake in comparison to the connected lake during the dry season. MeHg production exhibited a strong positive co-variation with cyanobacteria abundance (R(2)=0.78; p<0.0001 in dry; R(2)=0.40; p=0.029 in flood) and with total algal biomass (R(2)=0.86; p<0.0001), and a negative co-variation with Zygnemaphyceae (R(2)=0.50; p=0.0018) in the lake community in dry season. This indicates that ecological conditions that favour the establishment and development of cyanobacteria are associated with higher rates of methylation in aquatic systems. This suggests that cyanobacteria could be a proxy for sites of MeHg production in some natural aquatic environments.
汞（Hg）在水生系统中的毒性是由于甲基汞（MeHg）的存在和产生。最近在热带洪泛区环境中的研究表明，与水生植物根部相关的周丛生物会产生 MeHg。周丛生物群落是食物链的第一个环节，也是水生环境中 MeHg 的主要来源之一。这项工作的目的是检验以下假设：藻类群落结构会影响潜在的甲基化作用，并且具有不同藻类和细菌密度的生态上不同的群落直接影响大型植物根部 MeHg 的形成。为了评估这些假设，评估了与相关周丛藻类分类结构相关的凤眼莲根中的净 MeHg 生成。在旱季和雨季从潘塔纳尔（巴西）的两个洪泛区湖泊中采集了大型植物根样本。这些湖泊具有不同的生态条件，因为它们与巴拉圭河的侧向水力连通性在干旱时期有所不同。结果表明，洪季的 MeHg 生成量高于旱季。与连接的湖泊相比，在旱季，不连接的湖泊的 MeHg 生成速率更高。MeHg 生成率与蓝藻丰度呈强烈正协变（旱季 R(2)=0.78；p<0.0001；R(2)=0.40；p=0.029）和总藻类生物量（旱季 R(2)=0.86；p<0.0001），与Zygnemaphyceae 在旱季湖泊群落中呈负协变（R(2)=0.50；p=0.0018）。这表明有利于蓝藻建立和发展的生态条件与水生系统中更高的甲基化率有关。这表明在某些自然水生环境中，蓝藻可能是 MeHg 产生部位的替代指标。
