Warming, eutrophication (nutrient fertilization) and brownification (increased loading of allochthonous organic matter) are three global trends impacting lake ecosystems. However, the independent and synergistic effects of resource addition and warming on autotrophic and heterotrophic microorganisms are largely unknown. In this study, we investigate the independent and interactive effects of temperature, dissolved organic carbon (DOC, both allochthonous and autochthonous) and nitrogen (N) supply, in addition to the effect of spatial variables, on the composition, richness, and evenness of prokaryotic and eukaryotic microbial communities in lakes across elevation and N deposition gradients in the Sierra Nevada mountains of California, USA. We found that both prokaryotic and eukaryotic communities are structured by temperature, terrestrial (allochthonous) DOC and latitude. Prokaryotic communities are also influenced by total and aquatic (autochthonous) DOC, while eukaryotic communities are also structured by nitrate. Additionally, increasing N availability was associated with reduced richness of prokaryotic communities, and both lower richness and evenness of eukaryotes. We did not detect any synergistic or antagonistic effects as there were no interactions among temperature and resource variables. Together, our results suggest that (a) organic and inorganic resources, temperature, and geographic location (based on latitude and longitude) independently influence lake microbial communities; and (b) increasing N supply due to atmospheric N deposition may reduce richness of both prokaryotic and eukaryotic microbes, probably by reducing niche dimensionality. Our study provides insight into abiotic processes structuring microbial communities across environmental gradients and their potential roles in material and energy fluxes within and between ecosystems.

中文翻译：

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内华达山脉的高山湖泊微生物群落由温度，资源和地理位置组成。

变暖，富营养化（营养肥）和褐化（异源有机物负荷增加）是影响湖泊生态系统的三个全球趋势。然而，资源增加和变暖对自养和异养微生物的独立和协同作用尚不明确。在这项研究中，我们研究了温度，溶解有机碳（DOC，异源和本地）和氮（N）供应的独立和交互作用，以及空间变量对玉米的组成，丰富度和均匀度的影响。美国加利福尼亚内华达山脉中海拔和N沉积梯度下湖泊中的原核和真核微生物群落。我们发现原核和真核社区都是由温度构成的，陆地DOC和纬度。原核生物也受总DOC和水生（自生）DOC的影响，而真核生物也受硝酸盐的影响。此外，增加的氮利用率与原核生物群落的丰富度降低，以及真核生物的丰富度和均匀度降低有关。我们没有发现任何协同或拮抗作用，因为温度和资源变量之间没有相互作用。总之，我们的结果表明：（a）有机和无机资源，温度和地理位置（基于纬度和经度）独立地影响湖泊微生物群落；（b）由于大气中氮的沉积而增加的氮供应可能会降低生态位的维数，从而降低原核和真核微生物的丰富度。