Increased duration and frequency of droughts under global change may affect both temporary and formerly permanent watercourses. Streambed desiccation, cooccurring solar radiation, and high temperature all may affect the composition and metabolism of photoautotrophic organisms in benthic biofilms. To test these effects, we characterized the composition of pigments when biofilms were exposed to dry conditions, and compared this to pigments measured after flow resumed, as well as to others measured from permanent streams in the same region. This comparison revealed important differences in pigmentary composition based on flow conditions. Active chlorophylls decreased exponentially with the duration and severity of the nonflow period, while chlorophyll degradation products and protective carotenoids increased. Streams experiencing longer and more severe nonflow periods showed the highest dissimilarities in their biofilm pigmentary composition, and this pattern was maintained after flow resumed. Our results pointed to duration of nonflowing periods as the major driver of pigmentary composition, regardless of whether these were interrupted or not by short intervals of water flows. Multivariate changes in pigmentary composition between sampling periods highlighted the influence of the long-term hydrological history on the relative abundance of different taxonomic groups and their associated pigments. Overall, pigmentary fingerprints are informative of the biofilm capacity to resist water flow interruption and of their ability to recover after water flow returns.

中文翻译：

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临时流中的生物膜颜料表明干燥的持续时间和严重程度

全球变化下干旱持续时间和频率的增加可能会影响临时和以前永久的水道。河床干燥、同时发生的太阳辐射和高温都可能影响底栖生物膜中光合自养生物的组成和代谢。为了测试这些效果，我们表征了生物膜暴露在干燥条件下时颜料的组成，并将其与恢复流动后测量的颜料以及从同一区域的永久流中测量的其他颜料进行比较。这种比较揭示了基于流动条件的颜料组成的重要差异。活性叶绿素随着非流动期的持续时间和严重程度呈指数下降，而叶绿素降解产物和保护性类胡萝卜素增加。经历更长和更严重的非流动期的溪流在其生物膜色素组成方面表现出最大的差异，并且在恢复流动后仍保持这种模式。我们的结果表明，非流动期的持续时间是色素成分的主要驱动因素，无论这些是否被短时间间隔的水流中断。采样周期之间色素成分的多变量变化突出了长期水文历史对不同分类群及其相关色素相对丰度的影响。总的来说，色素指纹是生物膜抵抗水流中断的能力以及它们在水流返回后恢复的能力的信息。并且在流量恢复后保持这种模式。我们的结果表明，非流动期的持续时间是色素成分的主要驱动因素，无论这些是否被短时间间隔的水流中断。采样周期之间色素成分的多变量变化突出了长期水文历史对不同分类群及其相关色素相对丰度的影响。总的来说，色素指纹是生物膜抵抗水流中断的能力以及它们在水流返回后恢复的能力的信息。并且在流量恢复后保持这种模式。我们的结果表明，非流动期的持续时间是色素成分的主要驱动因素，无论这些是否被短时间间隔的水流中断。采样周期之间色素成分的多变量变化突出了长期水文历史对不同分类群及其相关色素相对丰度的影响。总的来说，色素指纹是生物膜抵抗水流中断的能力以及它们在水流返回后恢复的能力的信息。无论这些是否被短时间的水流中断。采样周期之间色素成分的多变量变化突出了长期水文历史对不同分类群及其相关色素相对丰度的影响。总的来说，色素指纹是生物膜抵抗水流中断的能力以及它们在水流返回后恢复的能力的信息。无论这些是否被短时间的水流中断。采样周期之间色素成分的多变量变化突出了长期水文历史对不同分类群及其相关色素相对丰度的影响。总的来说，色素指纹是生物膜抵抗水流中断的能力以及它们在水流返回后恢复的能力的信息。