互花米草入侵对滨海湿地甲烷厌氧氧化及其微生物机制影响研究

Anaerobic oxidation of methane (AOM) efficiently controls the CH4 emissions from the ocean, because almost all the CH4 produced in ocean sediments is consumed by AOM within the sulfate-penetrated seafloor zones. The invasion of exotic Spartina alterniflora has significantly increased CH4 emission from Chinese coastal wetlands. However, the emission rates are extremely lower than those from freshwater wetlands. The produced CH4 might be consumed by AOM process. However, there are still debates about the influence of S. alterniflora on AOM rates, and what is the microbiological mechanism for this important biochemical process controlling CH4 emissions. In this study, soil and porewater samples will be collected from open water, bare tidal flat, and invasive S. alterniflora, native Suaeda salsa, and Phragmites australis marshes. To understand the AOM rates in the coastal wetland and the their key affecting factors, anaerobic CH4 oxidation potential, CH4 production potential, concentrations of CH4 and electron acceptors (e.g. SO42-, NO2-, NO3-, Fe3+, MnO4-, et al.) will be analyzed. Laboratory incubation experiments, by using 13C isotope trace technique and molecular biotechnology such as DNA-SIP, will be carried out to investigate the association of AOM rates with the functional or community structure of the anaerobic methanotrophic archaea (ANME). The metabolic pathway of the functional ANME will explored by in situ identification of the ANME and their physically associated microorganisms by using the catalyzed reporter deposition fluorescent in situ hybridization (CARD-FISH). The objectives of this study are (1) to reveal the AOM rates in coastal wetlands and the implication to CH4 emissions, and (2) to gain a mechanistic understanding of invasive S. alterniflora on AOM process. This study will be exposed to provide scientific evidence for evaluation the impacts of S. alterniflora on CH4 emissions from coastal wetlands of China.

甲烷厌氧氧化是消减海洋甲烷排放的主要过程。互花米草入侵明显提高了滨海湿地甲烷排放，但排放量仍显著低于淡水湿地，产生的甲烷可能被厌氧氧化所消耗。那么，互花米草如何影响湿地甲烷厌氧氧化速率，微生物机制如何，尚不清楚。项目拟选取江苏大丰滨海湿地，采集互花米草、盐蒿、芦苇、光滩和开放水面湿地土壤，研究甲烷产生和厌氧氧化潜力及电子受体含量，阐明湿地甲烷厌氧氧化速率和互花米草入侵的影响效应，解析甲烷厌氧氧化的关键控制因素；采用13C示踪和稳定性同位素核酸探针(DNA-SIP)等技术，研究甲烷厌氧氧化菌数量和群落结构，阐明不同湿地甲烷厌氧氧化功能菌特征和互花米草入侵诱导的功能菌演替规律；利用酶联荧光原位杂交(CARD-FISH)技术，研究湿地甲烷厌氧氧化功能菌的原位分布特征及共生微生物种类和数量，解析甲烷厌氧氧化耦联代谢途径和互花米草入侵的影响机制，为评估互花米草入侵对滨海湿地甲烷排放影响提供科学依据。

项目围绕外来植物互花米草入侵对滨海湿地甲烷氧化的影响展开研究，重点研究了：（1）江苏盐城不同植被类型湿地甲烷好氧氧化速率和甲烷好氧氧化菌群落结构的差异；（2）外来植物互花米草入侵对滨海湿地厌氧甲烷氧化速率的影响及其微生物机制。研究工作紧紧围绕项目计划任务书载明的内容展开，已经达成预期目标。共发表SCI收录论文6篇，培养博士研究生2名，硕士研究生1名，博士后1名。主要进展如下：（1）利用二氟甲烷（CH2F2）抑制法和克隆文库技术，分别测定了滨海湿地甲烷好氧氧化速率和好氧甲烷氧化菌群落结构，发现互花米草湿地的甲烷好氧氧化速率分别是盐蒿湿地、芦苇湿地和光滩的1.98、1.10和4.59倍，优势甲烷好氧氧化菌由土著植物湿地的Type I和Type II型共同存在向米草湿地更适应于高O2环境的单一Type I型演替，表明互花米草入侵提升了湿地甲烷好氧氧化潜力；（2）利用13C示踪和454焦磷酸测序技术，发现互花米草入侵显著增加了滨海湿地厌氧甲烷氧化菌（ANME）尤其是ANME-2a-2b的相对丰度，导致米草湿地甲烷厌氧氧化速率是其他植被类型湿地的1.35-6.90倍。互花米草入侵导致的SOC和SO42-累积是刺激滨海湿地厌氧甲烷氧化菌演替和甲烷厌氧氧化速率增长的主要因素。互花米草入侵在增加滨海湿地甲烷产生潜力的同时，也同步增加了甲烷氧化速率，这在一定程度上限制了被入侵湿地甲烷排放的快速增长。