Abstract：
In glacier-fed streams, the Windows of Opportunity (WOs) are periods of mild environmental conditions supporting the seasonal development of benthic microorganisms. WOs have been defined based on changes in biofilm biomass, but the responses of microbial diversity to WOs in Alpine streams have been overlooked. A two year (2017-2018) metabarcoding of epilithic and epipsammic biofilm prokaryotes was conducted in Alpine streams fed by glaciers (kryal), rock glaciers (rock glacial), or groundwater/precipitation (krenal) in two catchments of the Central-Eastern European Alps (Italy), aiming at testing the hypothesis that: 1) environmental WOs enhance not only the biomass but also the α-diversity of the prokaryotic biofilm in all stream types, 2) diversity and phenology of prokaryotic biofilm are mainly influenced by the physical habitat in glacial streams, and by water chemistry in the other two stream types. The study confirmed kryal and krenal streams as endmembers of epilithic and sediment prokaryotic α- and β-diversity, with rock glacial streams sharing a large proportion of taxa with the two other stream types. Alpha-diversity appeared to respond to ecological WOs, but, contrary to expectations, seasonality was less pronounced in the turbid kryal than in the clear streams. This was attributed to the small size of the glaciers feeding the studied kryal streams, whose discharge dynamics were those typical of the late phase of deglaciation. Prokaryotic α-diversity of non-glacial streams tended to be higher in early summer than in early autumn. Our findings, while confirming that high altitude streams are heavily threatened by climate change, underscore the still neglected role of rock glacier runoffs as climate refugia for the most stenothermic benthic aquatic microorganism. This advocates the need to define and test strategies for protecting these ecosystems for preserving, restoring, and connecting cold Alpine aquatic biodiversity in the context of the progressing global warming.
摘要：
在冰川喂养的溪流中，机会之窗（WOS）是支持底栖微生物季节性发展的温和环境条件时期。基于生物膜生物量的变化定义了WOs，但是微生物多样性对高山溪流中WOs的反应却被忽视了。在冰川（kryal）喂养的高山溪流中进行了为期两年（2017-2018）的上皮性和表皮生物膜原核生物的元编码，岩石冰川（岩石冰川），或中东欧阿尔卑斯山（意大利）两个集水区的地下水/降水（krenal），旨在检验以下假设：1）环境WOs不仅增强了生物量，而且还增强了所有溪流类型中原核生物被膜的多样性，2)原核生物被膜的多样性和物候主要受冰川流物理生境的影响,以及其他两种类型的水化学。这项研究证实了kryal和krenal溪流是上皮性和沉积物原核a和b多样性的末端成员，岩石冰川溪流与其他两种溪流类型共享很大一部分分类单元。阿尔法多样性似乎对生态WOs做出了反应，但是,与预期相反,混浊的Kryal的季节性不如清澈的溪流明显。这归因于冰川的尺寸较小，这些冰川为所研究的克朗流提供了食物，其放电动力学是典型的冰消后期。非冰川流的原核生物a-多样性在初夏往往比初秋高。我们的发现,在确认高海拔溪流受到气候变化的严重威胁的同时，强调了岩石冰川径流作为大多数低温底栖水生微生物的气候避难所的作用。这主张需要定义和测试保护这些生态系统的策略，恢复,并在全球变暖的背景下连接寒冷的高山水生生物多样性。
