Data_Sheet_9_Forest zone and root compartments outweigh long-term nutrient enrichment in structuring arid mangrove root microbiomes.csv

Mangroves offer many important ecosystem services including carbon sequestration, serving as nursery grounds to many organisms, and acting as barriers where land and sea converge. Mangroves exhibit environmental flexibility and resilience and frequently occur in nutrient-limited systems. Despite existing research on mangrove microbiomes, the effects of nutrient additions on microbial community structure, composition, and function in intertidal and landward zones of mangrove ecosystems remain unclear. We utilized a long-term nutrient amendment study in Exmouth Gulf, Western Australia conducted in two zones, the intertidal fringe and supralittoral scrub forests, dominated by Avicennia marina. Root samples were fractionated into rhizosphere, rhizoplane and endosphere compartments and analyzed by 16S rRNA gene amplicon sequencing to determine the effects of nutrient stress on community structure and function. Our data showed species richness and evenness were significantly higher in the scrub forest zone. PERMANOVA analysis revealed a significant effect of nutrient enrichment on beta diversity (p = 0.022, R2 = 0.012) in the fringe forest zone only. Cylindrospermopsis, which has been associated with harmful algal blooms, was found to be significantly enriched in fringe phosphate-fertilized plots and nitrogen-fixing Hyphomicrobiales were significantly depleted in the scrub nitrogen-fertilized plots. Meanwhile, root compartments and forest zone had a greater effect on beta diversity (p = 0.001, R2 = 0.186; p = 0.001, R2 = 0.055, respectively) than nutrient enrichment, with a significant interaction between forest zone and root compartment (p = 0.001, R2 = 0.025). This interaction was further observed in the distinct divergence identified in degradative processes of the rhizosphere compartment between the two forest zones. Degradation of aromatic compounds were significantly enriched in the fringe rhizosphere, in contrast to the scrub rhizosphere, where degradation of carbohydrates was most significant. Despite the highly significant effect of forest zone and root compartments, the long-term effect of nutrient enrichment impacted community structure and function, and potentially compromised overall mangrove health and ecosystem stability.

红树林提供诸多重要生态系统服务，包括碳封存（carbon sequestration）、作为众多生物的育苗场，以及作为海陆交汇地带的防护屏障。红树林具备环境适应性与恢复力，常生存于营养限制生境中。尽管现有研究已关注红树林微生物组（mangrove microbiomes），但养分添加对红树林生态系统潮间带与陆向带微生物群落结构、组成及功能的影响仍不明确。本研究依托澳大利亚西部埃克斯茅斯湾（Exmouth Gulf）的长期养分添加实验，实验设置潮间带边缘林与潮上带灌丛林两个生境，优势物种均为白骨壤（Avicennia marina）。研究将根系样品划分为根际（rhizosphere）、根面（rhizoplane）与内生境（endosphere）三个组分，通过16S rRNA基因扩增子测序（16S rRNA gene amplicon sequencing）分析养分胁迫对微生物群落结构与功能的影响。数据显示，灌丛林生境的物种丰富度与均匀度显著更高。置换多元方差分析（PERMANOVA）结果表明，仅在边缘林生境中，养分富集对β多样性（beta diversity）存在显著影响（p=0.022, R²=0.012）。柱胞藻属（Cylindrospermopsis）——该类群与有害藻华（harmful algal blooms）相关——在边缘林磷酸盐施肥样地中显著富集；而固氮生丝单胞菌目（nitrogen-fixing Hyphomicrobiales）在灌丛林氮肥施肥样地中显著减少。同时，根系组分与生境类型对β多样性的影响（分别为p=0.001, R²=0.186；p=0.001, R²=0.055）均强于养分富集，且生境类型与根系组分间存在显著交互作用（p=0.001, R²=0.025）。这一交互作用进一步体现在两个生境的根际组分降解过程存在显著差异：边缘林根际的芳香族化合物降解显著富集，而灌丛林根际则以碳水化合物降解最为显著。尽管生境类型与根系组分对群落结构存在极显著影响，但长期养分富集仍会改变微生物群落结构与功能，或损害红树林整体健康与生态系统稳定性。