Temporary streams are submitted to high seasonal hydrological variations which induce habitat fragmentation. Global change promotes longer non-flow periods, affecting hydrological continuity and the distribution of biological assemblages in river networks. We aimed to investigate the effects of hydrological discontinuity on phototrophic biofilm assemblages in a Mediterranean stream, at both network and habitat scales. At the network scale during basal flow conditions, mostly nitrate and DOC concentrations were associated to the taxonomical and trait distribution of algae and cyanobacterial assemblages. Cyanobacteria dominated at the upstream and downstream sites of the network, while green algae and diatoms were abundant in its middle part. At the habitat scale, hydrological discontinuity promoted large changes in biofilm composition between riffles and pools, where pools were inhabited preferentially by green algae and riffle habitats by cyanobacteria. Our findings emphasize the myriad of factors affecting the spatial distribution of phototrophic biofilms, which become more heterogeneous according to water flow interruption. Under the predicted climate change scenarios, spatial heterogeneity in temporary streams may increase, which will lead to change phototrophic biofilm assemblages.

中文翻译：

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局部和区域环境因素驱动地中海河流光养生物膜组合的空间分布

临时河流受到季节性水文变化的影响，导致栖息地破碎化。全球变化导致更长的非流动期，影响水文连续性和河流网络中生物组合的分布。我们的目的是在网络和栖息地尺度上研究水文不连续性对地中海河流中光养生物膜组合的影响。在基流条件下的网络尺度上，大多数硝酸盐和 DOC 浓度与藻类和蓝藻组合的分类和性状分布有关。蓝藻在网络的上下游占主导地位，而绿藻和硅藻在网络中部丰富。在栖息地尺度上，水文的不连续性促进了浅滩和水池之间生物膜成分的巨大变化，其中水池优先栖息绿藻，浅滩栖息地则为蓝藻。我们的研究结果强调了影响光养生物膜空间分布的无数因素，根据水流中断，这些因素变得更加异质。在预测的气候变化情景下，临时河流的空间异质性可能会增加，这将导致光养生物膜组合的变化。