Mariculture Sludge Modifies Archaeal Community Diversity, Reduces Archaeal Variability, and Enhances Nitrogen Cycling Capacity in Paddy Soil

Given the increasing nitrogen losses in paddy soils associated with rice cultivation, this study employed 16S rRNA amplicon sequencing to investigate the effects of different concentrations of mariculture sludge on archaeal communities and nitrogen-cycling microorganisms. Mariculture sludge can enhance the α diversity of archaeal communities in paddy soil. The relative abundances of numerous archaeal taxa, such as Euryarchaeota and Woesearchaeota, were markedly higher in soils with the application of mariculture sludge than in those without mariculture sludge treatment, and the taxonomical distribution was significantly correlated with salinity, pH, NH₄⁺, PO₄³⁻ and TN. In terms of microecology, the application of mariculture sludge to paddy soil influenced the assembly of the archaeal community through deterministic processes; the average variation degree of the archaeal community decreased; and the predicted archaeal functions shifted toward nucleoside and nucleotide synthesis, amino acid synthesis, and carbohydrate synthesis. Mariculture sludge application resulted in a significant increase in the abundance of the mcrA gene (methane production) and decreases in the abundance of the amoA, pmoA, and mmoX genes (methane metabolism). Overall, mariculture sludge application enriched the archaeal community, reduced archaeal community variability and increased the potential for nitrogen cycling and biosynthesis in paddy soils. These results offer insights into the potential of mariculture sludge as an organic amendment for sustainable soil management, although further study is needed to assess its long-term effects on greenhouse gas emissions in paddy soil ecosystems.