Vertical Stratification in Composition, Metabolic Potential and Co-Occurrence Networks of Archaeal Communities in Mangrove Sediments, Zhanjiang, China.

Archaea, a pivotal domain in the global biosphere, serve as indispensable mediators in biogeochemical turnover of mangrove wetlands. Nonetheless, high-resolution vertical changes of archaeal communities, function, co-occurrence patterns, and assembly mechanisms as well as their driving factors are poorly described in the mangrove sediments. Herein, through high-throughput analysis of archaeal communities across seven depth intervals (0-90 cm) within 8 sediment cores collected in the Zhanjiang mangrove wetlands, we provide the vertical profiles of archaeal community composition and function, co-occurrence networks, and assembly mechanisms along the sediment depth. Our results show that archaeal abundance declined with sediment depths, while higher archaeal diversity was observed in the mangrove deep sediments. Thermoplasmatota was more abundant in surface mangrove sediments, whereas Thermoproteota (Bathyarchaeia) was remarkably enriched in deep sediments. Metabolically, surface archaeal communities are characterized by carbohydrate, amino acid, cofactor and vitamin metabolism, whereas glycan biosynthesis, xenobiotics biodegradation, and nucleotide metabolism serve as the predominant functions in deep archaeal communities. The surface network displayed greater complexity and stability than the deep counterpart, with Thermoproteota functioning as keystone taxa across all three networks. Further, stochastic processes govern archaeal community assembly in all sediment layers. Finally, sediment depth, temperature, moisture, TP, clay content, and salinity were identified as key drivers shaping archaeal communities. These findings expand our knowledge regarding the vertical distribution characteristics and key driving factors of mangrove archaea, while also underscoring their ecological importance in deep mangrove sediment habitats.