红树林凋落物分解过程硫酸盐还原微生物驱动的重金属归趋

Connecting the land and the sea, mangroves are key zones for immobilizing heavy metals. High productivity, elevated return rates, and extraordinary decomposition rates are some of the remarkable characteristics of the mangrove ecosystem. A large amount of litter production is an essential attribute of the mangrove system energy and matter flow. Microbial community succession occurs under the complex environmental gradients during the process of litter decomposition. However, little is known about the detailed succession process in the litter-sediment continuum, as well as the sulfur-reducing microorganism-drove heavy metal fate and its central control factor. This proposal proposes to characterize the spatiotemporal distribution patterns of the sulfur-reducing microorganism succession that occurs with the combing application of field experiment and dsrB sequencing-based community assembly, to reveal the role of sulfur-reducing microorganism on the migration behavior of heavy metals by the correlative analysis on sulfur-reducing microorganism community structure and heavy metal fates; to uncover the response characteristics of the migration of heavy metals driving by sulfur-reducing microorganism under various environmental conditions and ascertain the main driving factor through microcosm culture and stable isotopic probing. The forthcoming project will gain crucial information about the environmental fate of heavy metals at the litter-sediment continuum of the mangrove forests and provide a scientific basis for the control of heavy metal pollution for important ecological zones.

红树林湿地是衔接陆地-海洋重金属汇存的关键带。高生产力、高归还率、高分解率是红树林生态系统的显著特征，大量凋落物的生产是红树林系统的重要特点。微生物群落的结构和功能随着分解过程进行在各种复杂环境梯度下演替。目前对此过程中凋落物-沉积物连续体中微生物的演替过程仍未充分了解，同时也鲜有研究探讨此过程中硫酸盐还原微生物群落驱动的重金属归趋及其主控因子。本项目拟通过野外受控实验结合dsrB测序群落构建技术刻画凋落物分解过程硫酸盐还原微生物演替的时空模式，结合微生物群落结构的时空分布与重金属的归趋，揭示硫酸盐还原微生物群落对界面重金属迁移的影响；通过微宇宙培养结合稳定同位素探针技术，揭示硫酸盐还原微生物驱动的重金属迁移行为对多种环境条件的响应特征，解析凋落物分解过程重金属迁移的主控因子。本项目的开展可获取红树林凋落物-沉积物连续体重金属环境归趋的关键信息，为沿海区域重金属污染的合理控制提供科学依据。

红树林具有高生产力与高归还率，产生了大量的凋落物，这些凋落物在分解过程中微生物的演替过程及其驱动的异化硫酸盐还原如何影响重金属归趋仍未充分得到了解。本项目累计开展野外作业20余项50余人次，采集野外分解的凋落物样品95份，沉积物样品217份，完成285个扩增子的测序分析工作；搭建了室内潮汐模拟装置，开展了大量室内模拟实验，探讨了温度、淹水周期、水体硫酸盐浓度、As浓度等因子影响下硫酸盐的还原特征，对硫酸盐还原过程的生物标记物进行了初步筛选；收集室内模拟样品72份，完成了72个扩增子的测序分析工作。同时，与其他项目合作完成了台海两岸典型河口红树林湿地120份沉积物样品240个扩增子的测序分析工作；进行了红树林凋落物生产力的文献调研与数据编录，并初步扩展到其他潮间带植被类群，扩展了本成果的代表性；开发了基于18O的同位素探针技术的凋落物分解手段，发现了凋落物分解过程中DNA的同位素效应；初步量化了凋落物分解过程中硫酸盐还原微生物驱动重金属迁移的时空模式；基于dsrB功能基因扩增子测序刻画了影响硫酸盐还原微生物功能差异的主控环境因子及其对重金属迁移的影响；厘清了凋落物-沉积物界面上硫酸盐还原微生物群落结构的时空动态，结合铜在时空过程中的耦合变化，阐明了凋落物分解过程中痕量金属迁移的复杂动态。通过汇总这些进展，本项目有望为沿海区域重金属污染的合理控制提供科学依据。