| Soil salinization is one of the most serious long-term threats to the sustainability of land in the world.The exploration of efficient improvement and utilization of saline-alkali land resources is of great significance to achieving the goal of “land degradation neutrality by2030”.Periphyton is a complete and independent community structure,dominated by photooxygen communities,including algae,fungi,bacteria,protozoa,metazoa,and nonbiological components,such as soil,extracellular polymers and debris.Periphyton may be a new and promising biotechnology tool that can be used to improve the soil structure,reduce salinity and increase nutrient of coastal saline-alkali land.In this study,periphyton was selected as the test object.The ability of periphyton to improve coastal saline-alkali land was described by measuring the physical and chemical properties,enzyme activity,microbial diversity,and metagenomics.The purpose was to explore the effects and improvement mechanism of periphyton on coastal saline-alkali land.The main findings are as follows:1.The order of periphyton and soil salinity was: unplanted control soil > periphyton >soil under the periphyton.The order of periphyton and soil p H was: unplanted control soil >soil under the periphyton > periphyton.The organic matter content and enzyme activity of periphyton were significantly higher than that of soil.In the results of scanning electron microscopy,it was found that there was a large amount of sodium chloride on the surface of the periphyton.In addition,it was also discovered that periphyton had a special porous sponge-like structure formed by the polymerization of extracellular polysaccharides.2.The results of amplicon sequencing showed that periphyton had high bacterial richness and species diversity,and can promote the increase of the species abundance of the underlying soil and improve the composition of the microbial community.From the results of bacterial phyla level species composition,it can be seen that the top three bacterial phyla were Proteobacteria,Bacteroides and Chloroflexi.Among them,the abundance of Proteobacteria increased with the decrease of salinity.The abundance of fungal ITS and carbon fixation gene cbb M in the original saline soil was very low,and no corresponding fragments were amplified.The sequencing results of the nitrogen-fixing gene nif H showed that the relative abundance of Cyanobacteria in the periphyton was significantly higher than that in the unplanted control soil.Periphyton was identified as an important part of periphyton.3.Salt content,organic matter content,and enzyme activity were all significantly positively correlated with the relative abundance of Cyanobacteria,while p H value was significantly negatively correlated with the abundance of Cyanobacteria.The relative abundance of dominant bacteria with good ecological functions at the level of biological genus,including Salinarimonas,Hydrogenophaga,Lyngbya,and Oscillatoria,were also significantly positively correlated with organic matter content.4.The results of metagenomic functional gene annotation indicated that the metabolic pathway was the pathway with significant advantages in periphyton.In addition,the functions of periphyton in terms of cell activity and skeleton,cell membrane formation and defense mechanism were significantly higher than that of the unplanted control soil.Compared with soil,there were more resistance genes in periphyton,and the unique resistance genes can be assigned to Planctomycetes.The proportion of resistance genes assigned to Cyanobacteria and Gemmatimondete was greater than the proportion of their species annotations.The research results showed that periphyton could provide a more suitable environment and a rich source of nutrients for saline-alkali soils by adsorbing pollutants in the environment and increasing the diversity and richness of microbial communities.These results clarified the effect and mechanism of periphyton in improving coastal saline-alkali land and provide a theoretical basis. |
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