Streamflow, dissolved oxygen, and water temperature underpin stream fish habitat suitability, so climate change could cause widespread habitat deterioration. Identifying stream characteristics that mediate habitat resilience to heatwaves will allow conservation effort prioritisation. Here, a set of readily applied metrics were used to assess hydrological and oxythermal responses of neighbouring salmonid streams, with distinctive geologies, soil‐types, and localised riparian shading, to periods of anomalously warm conditions. During heatwaves, low flows, warm‐water temperatures, and diel oxygen variability, associated with biogenic production and respiration, predominated. In a low‐shade stream lacking significant catchment water storage, high daytime (>22°C) and night‐time (>19°C) water temperatures and low early morning O2 concentrations (<5 mg L−1) accumulated oxythermal stress for salmonids throughout summer. A stream with localised shading and a higher proportion of underlying aquifers and permeable soils throughout its watershed experienced considerably less cumulative oxythermal stress (O2 > 6 mg L−1; temperatures <19°C), whilst slower release of subsurface water bolstered base flows during dry spells. Our findings support conservation of shaded streams with permeable watersheds characterised by higher soil infiltration rates and aquifer storage capacity as salmonid sanctuaries under a warmer, drier summer climate. Preventing water quality and hydromorphological deterioration are paramount for safeguarding their role as climate refugia.

中文翻译：

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具有渗透性流域的阴凉溪流在热浪期间为鱼类提供了自然恢复力的栖息地

溪流、溶解氧和水温是溪流鱼类栖息地适宜性的基础，因此气候变化可能导致栖息地广泛恶化。确定调节栖息地抵御热浪能力的河流特征将有助于确定保护工作的优先顺序。在这里，使用一组易于应用的指标来评估邻近鲑鱼溪流的水文和氧热响应，这些溪流具有独特的地质、土壤类型和局部河岸阴影，对异常温暖条件时期的反应。在热浪期间，与生物生产和呼吸相关的低流量、温水温度和昼夜氧气变化占主导地位。在缺乏大量集水储水的低遮荫溪流中，白天 (>22°C) 和夜间 (>19°C) 水温较高，清晨 O2 较低2浓度（<5 mg·L−1）整个夏季鲑鱼都积累了氧热应激。一条具有局部阴影且整个流域内底层含水层和渗透性土壤比例较高的河流所经历的累积氧热应力（O2> 6 毫克/升−1;温度<19°C），而干旱时期地下水的缓慢释放增强了基流。我们的研究结果支持对具有渗透性流域的遮荫溪流进行保护，这些流域具有较高的土壤渗透率和含水层存储能力，可作为温暖、干燥的夏季气候下的鲑鱼保护区。防止水质和水貌恶化对于维护其作为气候避难所的作用至关重要。