PDF(Pubmed)
Abstract：
High turbidity and elevated water temperature are environmental stressors that can co-occur in freshwater ecosystems such as when deforestation increases solar radiation and sedimentary runoff. However, we have limited knowledge about their combined impacts on fish behaviour and physiology. We explored independent and interactive effects of sedimentary turbidity and temperature on the swimming activity and both thermal and hypoxia tolerance of the Pugnose Shiner (Miniellus anogenus, formerly Notropis anogenus), a small leuciscid fish listed as Threatened under Canada\'s Species at Risk Act (SARA). Fish underwent a 15-week acclimation to two temperatures (16°C or 25°C) crossed with two turbidities (~0 NTU or 8.5 NTU). Swimming activity was measured during the first 8 weeks of acclimation. Fish in warm water were more active compared to those in cold water, but turbidity had no effect on activity. Behavioural response to hypoxia was measured after 12 weeks of acclimation, as the oxygen level at which fish used aquatic surface respiration (ASR). Fish in warm water engaged in ASR behaviour at higher oxygen thresholds, indicating less tolerance to hypoxia. Turbidity had no effect on ASR thresholds. Finally, thermal tolerance was measured as the critical thermal maximum (CTmax) after 13-15 weeks of acclimation. Acclimation to warm water increased fish CTmax and Tag (agitation temperature) but reduced the agitation window (°C difference between Tag and CTmax) and thermal safety margin (°C difference between the acclimation temperature and CTmax). Furthermore, fish in warm, turbid water had a lower CTmax and smaller thermal safety margin than fish in warm, clear water, indicating an interaction between turbidity and temperature. This reduced thermal tolerance observed in Pugnose Shiner in warm, turbid water highlights the importance of quantifying independent and interactive effects of multiple stressors when evaluating habitat suitability and conservation strategies for imperilled species.
摘要：
高浊度和水温升高是淡水生态系统中可能同时发生的环境压力因素，例如当森林砍伐增加太阳辐射和沉积径流时。然而,我们对它们对鱼类行为和生理的综合影响的了解有限。我们探索了沉积浊度和温度对游泳活动以及PugnoseShiner（Miniellusanogenus，以前是Notropisanogenus)，根据加拿大的《危险物种法》(SARA)被列为受威胁的一种小白鱼。鱼经历了15周的适应，经历了两个温度（16°C或25°C），两个浑浊（〜0NTU或8.5NTU）。在适应的前8周测量游泳活动。与冷水中的鱼相比，温水中的鱼更活跃，但浊度对活性没有影响。适应12周后测量对缺氧的行为反应，作为鱼类使用水生表面呼吸（ASR）的氧气水平。温水中的鱼在较高的氧气阈值下从事ASR行为，表明对缺氧的耐受性较低。浊度对ASR阈值没有影响。最后,在适应13-15周后，将耐热性测量为临界热最大值（CTmax）。对温水的适应增加了鱼的CTmax和Tag（搅拌温度），但降低了搅拌窗口（Tag和CTmax之间的°C差）和热安全裕度（适应温度和CTmax之间的°C差）。此外，在温暖的鱼，浑浊的水比温暖的鱼有更低的CTmax和更小的热安全裕度，清澈的水,表明浊度和温度之间的相互作用。在温暖的情况下，在PugnoseShiner中观察到的耐热性降低，在评估栖息地适宜性和濒危物种的保护策略时，浑浊的水强调了量化多种压力源的独立和交互影响的重要性。
