Data_Sheet_1_Spatial patterns of benthic biofilm diversity among streams draining proglacial floodplains.pdf

Glacier shrinkage opens new proglacial terrain with pronounced environmental gradients along longitudinal and lateral chronosequences. Despite the environmental harshness of the streams that drain glacier forelands, their benthic biofilms can harbor astonishing biodiversity spanning all domains of life. Here, we studied the spatial dynamics of prokaryotic and eukaryotic photoautotroph diversity within braided glacier-fed streams and tributaries draining lateral terraces predominantly fed by groundwater and snowmelt across three proglacial floodplains in the Swiss Alps. Along the lateral chronosequence, we found that benthic biofilms in tributaries develop higher biomass than those in glacier-fed streams, and that their respective diversity and community composition differed markedly. We also found spatial turnover of bacterial communities in the glacier-fed streams along the longitudinal chronosequence. These patterns along the two chronosequences seem unexpected given the close spatial proximity and connectivity of the various streams, suggesting environmental filtering as an underlying mechanism. Furthermore, our results suggest that photoautotrophic communities shape bacterial communities across the various streams, which is understandable given that algae are the major source of organic matter in proglacial streams. Overall, our findings shed new light on benthic biofilms in proglacial streams now changing at rapid pace owing to climate-induced glacier shrinkage.

冰川退缩揭开崭新的冰前地貌，其沿纵向和横向年代序列展现出显著的环境梯度。尽管冰川前沿的溪流环境严酷，但其底栖生物膜却能够孕育出令人惊叹的生命多样性，跨越生命所有领域。在本研究中，我们探讨了在瑞士阿尔卑斯山三个冰前洪泛区，主要由地下水及融雪补给的多条交错式冰川径流支流中，原核生物和真核生物光合自养多样性的空间动态。沿着横向年代序列，我们发现支流中的底栖生物膜生物量高于冰川径流中的，且它们各自的多样性和群落组成存在显著差异。我们还观察到冰川径流中细菌群落沿纵向年代序列的时空更替。考虑到这些溪流之间紧密的空间邻近性和连通性，上述两种年代序列中的模式似乎出人意料，这表明环境过滤是潜在的机制。此外，我们的研究结果还表明，光合自养群落塑造了各条溪流中的细菌群落，这在逻辑上是可理解的，因为藻类是冰前溪流中有机物的主要来源。总体而言，我们的发现为因气候变化导致的冰川退缩而迅速变化的冰前溪流底栖生物膜提供了新的洞见。