Study On The Enrichment Characteristics Of Trace Elements In Submarine Cold Seep System And Their Coupling Relationship With Microorganisms

The migration of methane-rich fluids in seafloor cold seep drives strong microbial activities,among which the anaerobic oxidation of methane mediated by microorganisms is the most important biogeochemical process.At the same time,microbial-mediated methanogenesis and aerobic oxidation of methane will also occur.These processes provide the material and energy basis for the occurrence and development of the cold seep system.The study found that the anaerobic oxidation of methane can occur due to the use of many different electron acceptors,and many trace elements can participate in it as enzymatic cofactors,including Fe,Co,Ni,Zn,Mo,W,etc.;Methanogenesis can be regarded as the reverse reaction process of anaerobic methane oxidation,so both processes require the same combination of trace metal elements;and the aerobic oxidation process of methane has been widely concerned due to the discovery of its utilization of light rare earth elements,and the utilization of Cu is also present.But their specific coupling relationship is still unclear.In this paper,the cold seep sediments,sediment pore water and cold seep microbial communities developed in the Haima cold seep area of the South China Sea were used to study the ion concentration of pore water,the composition of microbial communities and the trace elements of sediment whole rock and lipid components.In order to identify the distribution characteristics of cold seep microbial communities,the geochemical and profile microbial taxa data of two cannulated sediments(ROV01-CS01,ROV01-CS03)at different depths in the Haima cold seep area were analyzed.We found that the SMTZ interface was identified as 15-20 cm for ROV01-CS01 and 30-35 cm for ROV01-CS03 and the sediments of the two cannula had significant geochemical gradients,and the cold seep activity was relatively stable.The microbial community composition also showed significant differences in the vertical depth profile,especially at the SMTZ interface,where the abundance of bacteria and archaea is 1-2 orders of magnitude higher than that of other layers.In the sediments above the SMTZ interface,sulfur oxidation and organic matter degradation are the main biogeochemical processes,while the layers below the SMTZ interface and below are dominated by the AOM-SR process coupled by SRB and ANME groups.In the case of high methane flux,the proportion of ANME-2 is higher than that of ANME-1,and ANME subgroups have different symbiotic relationships with different SRBs.Further research on the factors affecting microbial community composition is needed.In order to elucidate the coupling relationship between microbial activities and trace elements,the trace element contents of sediment whole-rock components and lipid components were analyzed,combined with microbial taxa in sediment profiles.The microbial community showed the predominant presence of SOB,SRB and ANME and a substantial enrichment of trace elements(Ni,Co,Cu,Zn,Mo,La,Ce,Pr,Nd)in the lipid fraction,which confirms their application as metalloenzymes in microbial processes related to methane metabolism in cold seep.In addition,due to the different time scales of different research carriers,the recorded information often does not match completely,which is of great significance for revealing the diversity of microbial communities in the cold seep area of the South China Sea and the coupling of microbial activities and trace elements.Based on the above research results,this paper conducted a geochemical study on the sediments developed in the cold seep area and profiled microbial groups,indepth discussion of the distribution characteristics of the cold seep microbial community,and proposed possible factors that caused the different distribution of the microbial community;and the coupling relationship between microbial activities and trace elements in the cold seep system was revealed through the study of biological groups and trace elements of lipid components in the sediment profile.The above findings provide a reliable scientific basis for understanding the coupling relationship between microbial activities and trace elements in cold seep systems,and further illustrate that there is still great potential for investigating the actual role of microbial activity on patterns and mechanisms of trace element incorporation into sediments in cold seep environments,which is likely to be a major factor in trace element enrichment.