Freshwater ecosystems are threatened by the global change-induced extreme climatic events worldwide. The unpredictable changes in water supply create strongly disturbed environments and ultimately result in diversity changes. Here, we studied the formation of benthic algal and cyanobacterial assemblages under intermediately disturbed (IDC) and highly disturbed conditions (HDC) in a small lowland intermittent stream. We addressed our hypotheses to the Intermediate Disturbance Theory supposing that intermediate frequencies or intensities of disturbances maximise diversity independently of its level. We expected a larger influence of extremes in water supply on functional than on taxonomic and phylogenetic diversity. Our results only partially proved our first hypothesis highlighting the (i) importance of short-time but intense disturbing effect on biofilm formation and trait composition under IDC period and (ii) the instability within the assemblages caused by large and opposing influences during HDC. Although extreme weather events caused trait extremes (supporting second hypothesis), they did not result in a decrease in functional richness (rejecting the second hypothesis). These findings in accordance with the insurance hypothesis clearly stress that a system with high functional redundancy can keep its functionality even under drastic hydrological conditions and the accompanying loss of species.

中文翻译：

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极端气候对低地间歇溪流中底栖藻类和蓝藻多样性的强烈影响

淡水生态系统受到全球变化引发的全球极端气候事件的威胁。供水中不可预测的变化会造成环境受到强烈干扰，并最终导致多样性的变化。在这里，我们研究了在小型低地间歇性溪流中中度扰动 (IDC) 和高度扰动条件 (HDC) 下底栖藻类和蓝藻组合的形成。我们针对中度干扰理论提出了假设，假设干扰的中频或强度最大化了多样性，而与其水平无关。我们预计供水极端对功能的影响大于对分类和系统发育多样性的影响。我们的结果仅部分证明了我们的第一个假设，强调了 (i) 在 IDC 期间对生物膜形成和性状组成的短期但强烈的干扰影响的重要性，以及 (ii) 在 HDC 期间由大而相反的影响引起的组合内的不稳定性。尽管极端天气事件导致性状极端（支持第二个假设），但它们并没有导致功能丰富度的下降（​​拒绝第二个假设）。这些符合保险假说的发现清楚地强调，即使在剧烈的水文条件和随之而来的物种丧失的情况下，具有高功能冗余的系统也能保持其功能。尽管极端天气事件导致性状极端（支持第二个假设），但它们并没有导致功能丰富度的下降（​​拒绝第二个假设）。这些符合保险假说的发现清楚地强调，即使在剧烈的水文条件和随之而来的物种丧失的情况下，具有高功能冗余的系统也能保持其功能。尽管极端天气事件导致性状极端（支持第二个假设），但它们并没有导致功能丰富度的下降（​​拒绝第二个假设）。这些符合保险假说的发现清楚地强调，即使在剧烈的水文条件和随之而来的物种丧失的情况下，具有高功能冗余的系统也能保持其功能。