Distribution Of Main Functional Gene Groups In Anaerobic Oxidation System Of Saltmarsh Soils At Elkhorn Slough

As a greenhouse gas with great warming potentiality,methane has aroused increasing attention in recent years.Wetland is the main source of methane emissions.Microorganisms including methanogens act as a leading factor in the mineralization process in the sedimentary environment of wetland ecosystems.In this paper,Yampah and Hudson,which locate in the salt marsh wetland of Elkhorn Slough on the east coast of the Pacific Ocean,were investigated.The abundance and distribution of two functional genes(methanogen function genes(mcrA)and sulfate-reducing bacteria functional genes(dsrA))in sedimentary environments were analyzed by means of real-time quantitative PCR.By investigating the changes of the abundance of two functional genes with depth in different sedimentary environments,the relationship between the copy number of functional genes of methanogens and sulfate reducing bacteria and soil physical and chemical factors was obtained.The following conclusions are drawn:1.Quantitative PCR analysis showed that differences in the horizontal distribution of the two functional genes were found.The functional gene mcrA of methanogens was detected only in some layers of tidal pools and high marshes,and the functional gene dsrA of sulfate reducing bacteria was detected only in non-vegetation zone,such as tidal pools and mudflats.2.Vertical distribution of the two functional genes also demonstrated spatial heterogeneity.In Yampah,the maximum concentration of mcrA appeared in the surface and bottom layer;in Hudson,the maximum concentration of mcrA gene appeared in the bottom layer.Overall,the concentration of mcrA peaked at depth of 11-13 cm.Different from the discontinuous distribution of mcrA,the distribution of dsrA with depth is continuous,and the concentrations of dsrA were found generally decreasing from the surface to the bottom.3.Site specific discriminations were found in the correlation between the two functional genes and environmental factors.The concentration of mcrA in tidal pool sediments of Yampah was not related to methane gas concentration and TOC.It was also not related to methane gas concentration in Hudson pool area.But it is positively related to TOC.The concentration of dsrA in Yampah pool area is not related to SD value,methane gas concentration and TOC.However,it was positively related to sulfate concentration.The concentration of dsrA in Hudson pool area is not related to SD value,sulfate concentration and methane gas concentration.It is positively related with TOC.In summary,methanogenesis and sulfate reduction occurred simultaneously in the saltmarsh soil.The high spatial heterogeneity of wetland methane production is affected by a variety of physical and chemical factors.Further exploration of functional bacteria such as methanogens and sulfate-reducing bacteria in wetlands has a great significance for revealing the mechanism of methane production in saltmarsh wetlands.