Effects Of Converting Typical Coastal Wetlands Into Aquaculture Ponds On Soil Carbon Pool And Microbial Characteristics In China

As one of the three major ecosystems of the earth,wetland plays a vital role in the sustainable development of the global environment,food supply,and maintenance of biodiversity.The specific objective of this study was to investigate the impact of wetlands utilization conversion on wetland ecosystem,thereby enriching the basic research in the field of microbiology and ecology of coastal wetlands in China.In this study,11 typical coastal wetlands in eastern China were used as research objects to analyze and compare the changes of soil physicochemical properties,nutrient content and organic carbon components before and after wetlands reclamation aquaculture,and used high-throughput sequencing technology to explore the response mechanism of soil microbial diversity and community structure to wetlands reclamation aquaculture,with a view to providing theoretical basis for the rational application and management of wetland resources,realizing an environment-friendly society,and maintaining multiple service functions of the wetland ecosystem.The main results are as follows:1.After the wetlands were reclaimed into aquaculture ponds,the soil bulk density of the whole section(0-30 cm)increased significantly(p<0.05),the electrical conductivity decreased to different degrees,the TP content did not change significantly(p>0.05),and the p H changes were different.After mangrove wetlands were reclaimed,the soil water content,TN content(except Pearl Bay)and AP content(except Dongzhai Port)of the whole soil profile decreased significantly(p<0.05).After reclamation of Suaeda salsa wetlands,the AP content of the whole soil profile increased significantly(p<0.05).Viewed from the vertical direction,soil AN content before and after wetlands reclamation aquaculture basically decreased with the increase of soil depth,and the phenomenon of surface accumulation appeared.2.Wetlands reclamation aquaculture changed the content of soil organic carbon different components to varying degrees,there was a certain correlation between the wetlands soil organic carbon components and environmental factors.The average soil SOC content of Suaeda salsa,Phragmites australis and mangrove wetlands decreased after reclamation.The average content of soil SOC in the upper layer(0-15 cm)decreased by 3.74%,23.22%and 46.19%,and the lower layer(15-30 cm)decreased by 17.11%,15.20% and 38.79%.The soil LOC content decreased after the mangrove wetlands reclamation.3.There was no significant change in the number of upper layer soil(0-15 cm)bacteria after the cultivation of Suaeda salsa and Phragmites australis wetlands(p>0.05),and the number of upper soil bacteria decreased after the mangrove wetlands reclamation.The number of fungi in the soil upper layer of the Suaeda salsa wetlands and Yancheng Phragmites australis wetlands were significantly reduced after reclamation(p<0.05).Only the fungus/bacteria ratio was not a strong indicator of the change in soil carbon pool stability.4.After wetlands reclamation aquaculture,the diversity and abundance of soil bacterial communities in the upper layer(0-15 cm)decreased,and the horizontal community composition of the bacteria phyla has not been significantly changed.The main dominant bacteria phyla were: Proteobacteria,Chloroflexi,Bacteroides,Acidobacteria and Firmicutes.Wetlands reclamation aquaculture changed the dominant bacterial genera in the soil.Wetland reclamation in Jiulongjiangkou and Dongzhai Port increased the relative abundance of Stenotrophomonas in the soil.Wetland reclamation in Dongzhai Port increased the relative abundance of Pseudomonas in the soil,and added Aeromonas.5.The impact of wetlands reclamation aquaculture in different regions on the diversity and abundance of upper layer(0-15 cm)soil fungal communities was inconsistent.The wetland reclamation of the Jiulongjiang Estuary had reduced the soil fungal diversity and richness.The wetland reclamation of the Yellow River Estuary and Dongzhaigang had significantly increased the soil fungal diversity and abundance.Before and after the wetlands reclamation,the soil Ascomycota had an absolute advantage,but its relative abundance decreased significantly after the reclamation.The reclamation changed the community composition of soil fungi at genus level.The reclamation of the Yellow River Estuary wetland caused the disappearance of Emericellopsis,Mucor,and Acremonium.The wetland reclamation of Jiulongjiang Estuary and Dongzhai Port significantly reduced the relative abundance of Penicillium,and added Fusarium,meanwhile Alternaria was added after the Jiulong River Estuary wetland reclamition.6.Environmental factors had a significant impact on the relative abundance of wetlands soil bacteria and fungi.Stenotrophomonas had a significant negative correlation with water content(p<0.05),and a significant positive correlation with bulk density and p H(p<0.01);Sulfurimonas,Woeseia and other bacterial genera had a significant negative correlation with soil bulk density(p<0.01);Penicillium had a significant negative correlation with bulk density(p<0.05),and significant negative correlation with p H(p<0.01),and significant positive correlation with total organic carbon content(p<0.01);Emericellopsis was significantly positively correlated with bulk density and p H(p<0.05),and significantly negatively correlated with total organic carbon content(p<0.01).