脉冲式盐水及Fe(III)施加对河口感潮淡水湿地土壤产甲烷菌和硫酸盐还原菌群落结构和数量的影响

以闽江河口塔礁洲感潮淡水河岸野慈姑（Sagittaria trifolia Linn.）沼泽湿地为研究对象，通过连续一年每月脉冲式施加人造海水和Fe（OH）₃溶液，研究了脉冲式盐水入侵和Fe（III）浓度增强对河口感潮沼泽湿地土壤产甲烷菌和硫酸盐还原菌群落结构的影响.结果显示，单独Fe（III）施加显著提高了土壤Fe（III）含量，单独盐水施加提高了土壤电导率及间隙水SO₄^2-、Cl^-和NH₄⁺浓度，在Fe（III）和盐水交互作用下间隙水NO₃^-浓度显著降低.土壤产甲烷菌主要包括甲烷微菌目（Methanomicrobiales）、八叠球菌目（Methanosarcinales）、甲烷杆菌目（Methanobacteriales）和Methanomassiliicoccales，硫酸盐还原菌主要有脱硫弧菌目（Desulfovibrionales）、脱硫杆菌目（Desulfobacterales）、互营杆菌目（Syntrophobacterales）和梭菌目（Clostridiales）.无论是脉冲式盐水入侵、Fe（III）浓度增强或是两者交互作用对于土壤产甲烷菌和硫酸盐还原菌多样性及群落结构的影响均不显著.与目水平相比，硫酸盐还原菌在属水平上对于各添加处理的响应更为明显，其中盐水+Fe（III）处理下Desulfatibacillum和Desulfovirga的相对丰度明显增加.RDA分析表明，土壤电导率对产甲烷菌群落结构的影响最为显著，Fe（III）是影响硫酸盐还原菌的重要环境因子，且Desulfatibacillum、Desulfobulbus、Desulfovirga等菌属对环境因子的响应较为敏感.研究表明，脉冲式盐水入侵及三价铁浓度增加对于我国东南沿海河口感潮淡水沼泽湿地土壤产甲烷菌和硫酸盐还原菌无显著影响.

Effects of saltwater and Fe(III) pulses on community structure and abundance of methanogens and sulfate-reducing bacteria in tidal freshwater marsh of the Min River estuary

By monthly in-situ experimental manipulations of the additions of saltwater and Fe(III) within a tidal freshwater wetland dominated by Sagittaria trifolia Linn. in the Min River estuary, southeast China over one year, the effects of saltwater intrusion pulse and Fe(III) addition on the community structure and abundance of methanogens and sulfate-reducing bacteria (SRB) of the tidal freshwater marsh were determined. The results showed that individual Fe(III) addition significantly increased the soil Fe(III) content, while saltwater intrusion increased the conductivity of the soil and the concentration of SO₄^2-, Cl^- and NH₄⁺ in the pore water, and the combined saltwater and Fe(III) additions significantly decreased the concentration of NO₃^-. The observed methanogens mainly included Methanomicrobiales, Methanosarcinales, Methanobacteriales, and Methanomassiliicoccales. SRB mainly included Desulfovibrionale, Desulfobacterales, Syntrophobacterales, and Clostridiales. Neither saltwater pulse intrusion, increased Fe(III) concentration, nor their interaction had significant effects on the diversity and community structure of methanogens and SRB in the soil. Compared with the order level, the changes at the genus level were more obvious, where the relative abundance of Desulfatibacillum and Desulfovirga increased significantly under saltwater+Fe(III) treatment. RDA analysis showed that the soil electrical conductivity had the most significant influence on the community structure of methanogens, Fe(III) was an important environmental factor affecting SRB, and Desulfatibacillus, Desulfobulbus, Desulfovirga were sensitive to environmental factors. The results indicated that the short-term pulsed saltwater intrusion and Fe(III) addition had no significant effect on methanogens and SRB in tidal freshwater marshes in southeast China.