| CH4 is the second greenhouse gas in the atmosphere, and its warming effect is about 28 times than CO2 at the same volume. As a result, CH4 has a strong influence for the global greenhouse effect. Therefore, it is significant to study methane-oxidation process, understand the mechanism of methane-oxidation and find out the effective measures to decrease the atmospheric methane concentration. In this study, we chose a typical Spartina alterniflora invasion smarsh as our study site which located in Yancheng City, Jiangsu Province. We still chose another three different native vegetation wetlands at the same location including Phragmites australis, Suaeda salsa and bare tidal flat as the control. We measured methane oxidation rate by laboratory incubation experiment under both the aerobic and anaerobic condition. Furthermore, we have used the molecular biology technology of 454 high-throughput sequencing to analyze the archaeal 16 S r RNA gene about methane anaerobic oxidation, and also used gene clone library to analyze methane-oxidizing bacteria pmo A gene. The results can provide some references for researching and estimating the change of methane oxidation rate and methane oxidation microbes under Spartina alterniflora invasion in coastal wetlands.The soil samples were collected from 4 vagetation wetlands of Spartina alterniflora, Phragmites australis, Suaeda salsa and bare tidal flat and all were located in Yancheng City, Jiangsu Province. We have cultivated soil sample for 10 days by adding CH2F2, cutting off air completely and controlling the soil and water ratio to measure aerobic oxidation rate under lab condition. The results indicate that different vegetation has a different rate, but there is a similar change tendency of methane oxidation rate in all treatments. The methane oxidation rate range about S. alterniflora is 0.11~ 1.77 μg CH4 g-1 h-1, the wetland of S. salsa is 0.33~ 1.37 μg CH4 g-1 h-1, P. australis is 0.06~ 2.30 μg CH4 g-1 h-1, and bare tidal is 0.24~ 2.21 μg CH4 g-1 h-1, respectively. The net average methane oxidizing rate of S. alterniflora is 1.01 μg CH4 g-1 h-1, what is 1.98, 1.10 and 4.59 times than P. australis, S. salsa and bare tidal respectively. Two- factor correlation analysis of arobic methane oxidaxing rate with soil properties shows that the oxidizing rate has a significant linear relationship with SOC, TN, SO42- concentration and salinity(P<0.05), while the methane aerobic oxidizing rate of S. alterniflora wetland is easily influenced by soil properties.Phylogenetic tree of pmo A gene shows that all the advantage methanotrophic for different wetlands were belonged to Type I bacteria, and all the rest of Type II bacteria belonged to Methylocystis. All methanotrophic of S. alterniflora belonged to Type Ia and 25.0% were classified to UCS γ. Mostly of S. salsa belongs to Methylosarcina、Methylobacter、Methylococcaceae and Methylohalobius. 85.7% of P. australis belonged to Methylomicrobium, Methylobacter and Methylococcaceae. Bare tidal with higher diversity than other were classified to 6 genus. Principal coordinate analysis(PCo A) of pmo A genes indicates that arobic methanotrophical community of S. alterniflora wetland has a significant difference with other 3 coastal wetlands. Redundancy analysis(RDA) of arobic methanotrophical community with soil properties shows that SOC, TN, salinity and sulfate co ncentrations are the main factors affected the Type Ia methanotroph, while the p H has a singnificant impact by Type Ib and Type II methanotroph.The incubation for anaerobic oxidation rate has cultivated for 45 days by adding CH2F2, cutting off air completely, Charging with N2 to replace air and controlling the soil and water ratio. The results of incubation experiment indicate that the oxidizability of S. alterniflora was different with others. The anaerobic oxidation rate of S. alterniflora ranged in 0.04~ 41.66 μg CH4 g-1 d-1, the wetland of S. salsas was:-0.06~ 19.57 μg CH4 g-1 d-1, P. australis was-1.24~ 38.39 μg CH4 g-1 d-1,and bare tidal was-1.85~ 27.57 μg CH4 g-1 d-1. The net average methane anaerobic oxidizing rate of S. alterniflora is 6.74 μg CH4 g-1 d-1, what is 6.90, 1.51 and 1.35 times than P. australis, S. salsa and bare tidal respectively. Two- factor correlation analysis of anarobic methane oxidaxing rate with soil properties shows that the oxidizing rate has a significant linear relationship with SOC, SO42- concentration(P<0.05) in coastal wetlands. S. alterniflora accumulated SOC and SO42- through its huge roots’ system, what makes the anaerobic CH4 oxidation rate significantly higher than other vegetation.The analyze of archaeal 16 S r RNA genes for coastal wetlands showed that the sequences associated with ANMEs were Methanosarcinale, Methanobacterium, Methanococcoides and Methanosarcina through 454 high-throughput sequencing The obtained sequences held a higher genetic relationship with ANMEs which were belonged to ANME-1、ANME-2a-2b and ANME-2d. At the same time, we also got the sulfate-reducing bacteria community which couple with the methane anaerobic oxidizing process including: Desulfobacterales, Desulfuromonadales a nd Desulfobulbaceae in bare tidal and P. australis. Hence, we speculated that sulfate-reducing coupled with anaerobic methane oxidation process was the major pathway in bare tidal and P. australis. We assume that it still has another pathway for S. salsas wetland and P. australis wetland to oxidating methane, but we couldn’t find the bacteria belong to NC10 phylum. Redundancy analysis(RDA) of anarobic methanotrophical community with soil properties shows that both ANME-2a-2b and Methanobacterium are easily impacted by salinity and SO42-.The soil properties are main factors to influnce ANMEs and SBR community structure in coastal wetlands.Our research described the influence of aerobic methane oxidation and anaerobic methane oxidation rate about S. alterniflora invasion for coastal wetlands. Meanwhile, we also illustrated the changes about the abundance and community structure with bacteria pmo A gene and archaeal 16 S r RNA genes caused by S. alterniflora invasion. Basing on our results, we summarized that the community structure and diversity of aerobic and anaerobic methanotrophs have been changed by S. alterniflora invasion. It directly influenced the abundance and oxidizing ability of methane oxidation microbes. Finally, the exotic of S. alterniflora invasion can make a significant difference about methane oxidating rate and methanotrophical structures of different vegetation in coastal wetlands. |
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