School of Biological Science, The University of Queensland, Brisbane, QLD 4072, Australia
School of Biological Science, The University of Queensland, Brisbane, QLD 4072, Australia.
J Exp Biol. 2020 Aug 21;223(Pt 16):jeb224444. doi: 10.1242/jeb.224444.
Rising temperatures are set to imperil freshwater fishes as climate change ensues unless compensatory strategies are employed. However, the presence of additional stressors, such as elevated nitrate concentrations, may affect the efficacy of compensatory responses. Here, juvenile silver perch () were exposed to current-day summer temperatures (28°C) or a future climate-warming scenario (32°C) and simultaneously exposed to one of three ecologically relevant nitrate concentrations (0, 50 or 100 mg l). We measured indicators of fish performance (growth, swimming), aerobic scope (AS) and upper thermal tolerance (CT) to test the hypothesis that nitrate exposure would increase susceptibility to elevated temperatures and limit thermal compensatory responses. After 8 weeks of acclimation, the thermal sensitivity and plasticity of AS and swimming performance were tested at three test temperatures (28, 32, 36°C). The AS of 28°C-acclimated fish declined with increasing temperature, and the effect was more pronounced in nitrate-exposed individuals. In these fish, declines in AS corresponded with poorer swimming performance and a 0.8°C decrease in CT compared with unexposed fish. In contrast, acclimation to 32°C masked the effects of nitrate; fish acclimated to 32°C displayed a thermally insensitive phenotype whereby locomotor performance remained unchanged, AS was maintained and CT was increased by ∼1°C irrespective of nitrate treatment compared with fish acclimated to 28°C. However, growth was markedly reduced in 32°C-acclimated compared with 28°C-acclimated fish. Our results indicate that nitrate exposure increases the susceptibility of fish to acute high temperatures, but thermal compensation can override some of these potentially detrimental effects.
气温上升将危及淡水鱼类，除非采取补偿策略应对气候变化。然而，额外的胁迫因素的存在，如硝酸盐浓度升高，可能会影响补偿反应的效果。在这里，银鲈（）幼鱼暴露在当前夏季温度（28°C）或未来气候变暖情景（32°C）下，同时暴露在三种生态相关硝酸盐浓度（0、50 或 100 mg l）之一中。我们测量了鱼类表现（生长、游泳）、有氧范围（AS）和上热耐受（CT）的指标，以检验硝酸盐暴露会增加对高温的敏感性并限制热补偿反应的假设。在 8 周的适应期后，在三个测试温度（28、32、36°C）下测试了 AS 和游泳性能的热敏感性和可塑性。28°C 适应的鱼的 AS 随温度升高而下降，在硝酸盐暴露的个体中更为明显。在这些鱼中，AS 的下降与游泳性能的下降以及 CT 下降 0.8°C 相对应，与未暴露的鱼相比。相比之下，适应 32°C 掩盖了硝酸盐的影响；与适应 28°C 的鱼相比，适应 32°C 的鱼表现出热不敏感表型，即无论硝酸盐处理如何，运动表现保持不变，AS 维持，CT 增加约 1°C。然而，与适应 28°C 的鱼相比，适应 32°C 的鱼的生长明显减少。我们的结果表明，硝酸盐暴露会增加鱼类对急性高温的敏感性，但热补偿可以克服其中一些潜在的有害影响。
