3Rs of drought: resistance, resilience and recovery - an opportunistic experiment

2022年夏天，英格兰有史以来最高的气温和自1935年以来最低的7月降雨量。这场干旱是欧洲500年来最严重的一次，导致英格兰和威尔士大部分地区的河道普遍干涸。虽然在历史上是极端的，但干旱预示了气候变化的预期条件：这种极端的水文气候事件预计将在未来变得更加频繁。我们预测这种干旱对生活在河流中的生物群落的影响，从而减轻最严重影响的能力受到限制，因为我们对影响它们抵御干旱影响和恢复水流后恢复能力的因素了解有限。在这里，河床的底质特别重要，因为一旦失去地表水，许多动物就会退回到潮湿的地下底质中。如果不清楚底质特征如何影响河流对干旱的反应，河流管理者就不能优先考虑保护最脆弱的河流免受干旱。我们处于一个独特的位置，已经在多个复制的河流通道中建立了一个实验，这将使我们能够通过实验研究基质/细沉积物对河流社区对干旱的反应以及恢复流动后恢复和恢复的潜力的影响。该实验旨在研究基质成分和细沉积物负荷对大型无脊椎动物群落的影响，随着干旱期间水位的下降，这些处理措施自然干燥。我们将探讨基质特性如何影响i）无脊椎动物在河床中持续干旱的能力，ii）无脊椎动物一旦流量恢复，通过从河床中出现来使河流酸化的能力，以及iii）与其他殖民路线（空中或漂流）相比，从河床酸化的相对重要性。

The summer of 2022 has seen the highest air temperatures ever recorded in England and the lowest July rainfall since 1935. This drought, the worst in Europe for 500 years, has resulted in the widespread drying of river channels over large parts of England and Wales. Whilst extreme in historic terms, the drought provides a foretaste of the conditions expected with climate change: such extreme hydroclimatic events are expected to become more frequent in the future. Our ability to predict the impact of such droughts on the biological communities living in rivers, and hence mitigate the most severe effects, is constrained by a limited understanding of the factors influencing their abilities to resist the effects of drought and to recovery once flow resumes. Here the substrate of the river bed is particularly important, as many animals will retreat into wet subsurface substrate once surface water has been lost. Without a clear understanding of how substrate characteristics affect the response of rivers to drought, river managers cannot prioritize the most vulnerable rivers for protection from drying. We are in a unique position of having an experiment already set up in multiple replicated stream channels that will enable us to experimentally examine the effects of substrate/fine sediment on the response of river communities to drought and on their potential to recolonise and recover following the resumption of flow. The experiment, set up to look at the effects of substrate composition and fine sediment loading on the macroinvertebrate communities dried naturally as water levels declined during the drought, with the treatments left in situ. We will explore how substrate characteristics influence i) the ability of invertebrates to persist through drought in the river bed, ii) the ability of invertebrates to recolonise the river by emerging from the river bed once flow resumes, and iii) the relative importance of recolonisation from the river bed compared with other routes of colonization (aerial or drifting).