Microbiology of wetlands and the carbon cycle in coastal wetland mediated by microorganisms.

Wetlands are highly diverse and productive and are among the three most important natural ecosystems worldwide, among which coastal wetlands are particularly valuable because they have been shown to provide important functions for human populations. They provide a wide variety of ecological services and values that are critical to humans. Their value may increase with increased use or scarcity owing to human progress, such as agriculture and urbanization. The potential assessment for one coastal wetland habitat to be substituted by another landscape depends on analyzing complex microbial communities including fungi, bacteria, viruses, and protozoa common in different wetlands. Moreover, the number and quality of resources in coastal wetlands, including nutrients and energy sources, are also closely related to the size and variety of the microbial communities. In this review, we discussed types of wetlands, how human activities had altered the carbon cycle, how climate change affected wetland services and functions, and identified some ways to promote their conservation and restoration that provide a range of benefits, including carbon sequestration. Current data also indicated that the coastal ocean acted as a net sink for atmospheric carbon dioxide in a post-industrial age and continuous human pressure would make a major impact on the evolution the coastal ocean carbon budget in the future. Coastal wetland ecosystems contain diverse microbial communities, and their composition of microbial communities will tend to change rapidly in response to environmental changes, as can serve as significant markers for identifying these changes in the future.

Composition and assembly mechanisms of prokaryotic communities in wetlands, and their relationships with different vegetation and reclamation methods.

Coastal wetlands are undergoing substantial transformations globally as a result of increased human activities. However, compared to other ecosystems, diversity and functional characteristics of microbial communities in reclaimed coastal wetlands are not well studied compared to other ecosystems. This is important because it is known that microorganisms can play a crucial role in biogeochemical cycling within coastal wetland ecosystems. Hence, this study utilized the high-throughput sequencing technique to investigate the structure and assembly processes of microbial communities in reclaimed coastal wetlands. The results revealed a substantial change in soil properties following coastal wetland reclamation. Remarkably, the reclaimed soil exhibited significantly lower pH, soil organic carbon (SOC), and total salinity (TS) values (p < 0.05). The dominant phyla included Proteobacteria, Chloroflexi, Bacteroidetes, Acidobacteria, and Planctomycetes among study sites. However, the relative abundance of Proteobacteria increased from un-reclaimed coastal wetlands to reclaimed ones. The Proteobacteria, Chloroflexi, and Acidobacteria showed higher relative abundance in vegetated soil compared to bare soil, while Bacteroidetes and Planctomycetes exhibited the opposite trend. Notably, vegetation types exerted the strongest influence on microbial diversity, surpassing the effects of soil types and depth (F = 34.49, p < 0.001; F = 25.49, p < 0.001; F = 3.173, p < 0.078, respectively). Stochastic assembly processes dominated in un-reclaimed soil, whereas deterministic processes governed the assembly in artificial sea embankment wetlands (SEW). The presence of Spartina alterniflora in all soil types (except SEW soils) indicated stochastic assembly, while Phragmites australis in reclaimed soils pointed toward deterministic microbial assembly. Furthermore, environmental factors such as pH, soil water content (SWC), SOC, total carbon (TC), total nitrogen (TN), total phosphorus (TP), NH4+-N, vegetation types, soil depth, and geographic distance exhibited significant effects on microbial beta diversity indices. Co-occurrence network analysis revealed a stronger association between taxa in SEW compared to land reclaimed from wetlands (LRW) and natural coastal wetlands (NCW). The bottom soil layer exhibited more complex network interactions than the topsoil layer. Besides soil parameters, reclamation and varieties of vegetation were also substantial factors influencing the composition, diversity, and assembly processes of microbial communities in coastal wetlands.