Sandy sediments of lowland streams are typically transported at low flow in the form of migrating ripples. In these bedforms, microbial communities spanning all trophic guilds (heterotrophic bacteria, fungi, photoautotrophic and phagotrophic protists) are exposed to highly frequent moving–resting cycles of sediment grains. Up to date, it is unknown to what extent ripple migration impacts community metabolism and composition as well as the vertical zonation of sediment‐associated multitrophic microbial communities compared to stationary sediments. We hypothesize that, as a result of mechanical abrasion and limited light supply, migrating ripple sediments have lower microbial abundance, diversity, metabolism and resource acquisition and no vertical zonation compared to stationary sediments. We collected samples from five lowland streams in north‐eastern Germany between May and June 2020. The coarser and better sorted sediments of migrating ripples had a higher oxygen concentration and less organic matter than stationary sediments. Photosynthetic pigments, potential extracellular enzyme activities, bacterial cell counts, and fungal gene copies were lower in migrating ripples than in stationary sediments. In contrast, cell‐specific bacterial production was higher in migrating ripples. Metabarcoding revealed that bedform migration was important in shaping the community structure of bacteria, fungi, and phagotrophic protists. Dry mass‐related net community production, respiration, and bacterial production were higher in superficial compared to underlying layers irrespective of sediment transport. By modulating the abundance, diversity, and structure of different trophic guilds of microbial communities and their resource acquisition, migrating bedforms create streambed heterogeneity, shaping regional biodiversity and the flow of matter through the benthic food web.

中文翻译：

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迁移的涟漪产生河床异质性，改变微生物多样性和代谢活动


低地溪流的沙质沉积物通常以迁移波纹的形式以低流量输送。在这些床型中，跨越所有营养群（异养细菌、真菌、光合自养和吞噬原生生物）的微生物群落暴露于沉积物颗粒的频繁移动-静止循环中。迄今为止，与静止沉积物相比，尚不清楚波纹迁移在多大程度上影响群落代谢和组成，以及与沉积物相关的多营养微生物群落的垂直分区。我们假设，由于机械磨损和有限的光照，与静止沉积物相比，迁移的波纹沉积物具有较低的微生物丰度、多样性、新陈代谢和资源获取，并且没有垂直分区。我们于 2020 年 5 月至 6 月期间从德国东北部的 5 条低地溪流收集了样本。与静止沉积物相比，迁移波纹的较粗且分选较好的沉积物具有更高的氧浓度和更少的有机物。迁移波纹中的光合色素、潜在的细胞外酶活性、细菌细胞计数和真菌基因拷贝均低于静止沉积物中的水平。相比之下，迁移波纹中细胞特异性细菌的产量更高。元条形码揭示床型迁移对于塑造细菌、真菌和吞噬原生生物的群落结构非常重要。无论沉积物运输如何，与干物质相关的净群落生产、呼吸和细菌生产在表层均高于下层。 通过调节微生物群落不同营养群的丰度、多样性和结构及其资源获取，迁移床形创造了河床异质性，塑造了区域生物多样性和通过底栖食物网的物质流动。