Quantifying the contribution of the rare biosphere and functional potential to the compacted clay baseliner of sanitary landfill
摘要
Compacted clay liners (CCLs) are crucial for limiting leachate migration in landfills; however, their long-term stability may be compromised. This study at the Pulau Burung Sanitary Landfill (PBSL), Penang, Malaysia, quantified microbial community dynamics in CCLs, focused on rare and low-abundance taxa and their functional potential. Seasonal communities were profiled via 16 S rRNA gene sequencing and PICRUSt2 functional predictions. Environmental parameters and geotechnical properties remained stable, with only minor changes in microbial community structure and no significant differences in α- and β-diversity (p> 0.05). Abundant taxa contributed ~ 52% to β-diversity variation, while low-abundance and rare taxa contributed ~ 5.1% and ~ 42.9%, respectively. Dominant phyla included Pseudomonadota (37.1%), Actinomycetota (16.2%), Bacteroidota (12.7%), and Bacillota (8.6%). Rare and low-abundance groups, such as Desulfobacterota and Nanoarchaeota, exhibited heightened sensitivity to environmental stress. Partitioning of β-diversity indicated that abundant taxa explained ~ 65% of community heterogeneity, low-abundance taxa ~ 20%, and rare taxa ~ 15%. Functional inference implicated rare sulfate-reducing, iron-reducing, and EPS-producing taxa in the CCL. Prominent genera included Marinobacter, Acidiphilium, Pseudomonas, and Halomonas, with rare taxa cumulatively contributing ~ 17.5%. Statistical analyses (ANOVA with Benjamini–Hochberg correction) revealed significant differences in functional group abundances (p < 0.05), and permutation tests confirmed that rare taxa disproportionately influence predicted functions (p < 0.05). These results indicated that rare and low-abundance microbial taxa may influence the compacted clay liner performance. Their functional roles, despite limited abundance, warrant consideration in engineered barrier assessments due to their ecological and structural impact.