Effects of hypoxia and ocean acidification on the upper thermal niche boundaries of coral reef fishes

Rising ocean temperatures are predicted to cause a poleward shift in the distribution of marine fishes occupying the extent of latitudes tolerable within their thermal range boundaries. A prevailing theory suggests that the upper thermal limits of fishes are constrained by hypoxia and ocean acidification. However, some eurythermal fish species do not conform to this theory, and maintain their upper thermal limits in hypoxia. Here we determine if the same is true for stenothermal species. In three coral reef fish species we tested the effect of hypoxia on upper thermal limits, measured as critical thermal maximum (CTmax). In one of these species we also quantified the effect of hypoxia on oxygen supply capacity, measured as aerobic scope (AS). In this species we also tested the effect of elevated CO2 (simulated ocean acidification) on the hypoxia sensitivity of CTmax. We found that CTmax was unaffected by progressive hypoxia down to approximately 35 mmHg, despite a substantial hypoxia-in...

据预测，海洋升温将导致栖息于自身温度耐受范围边界内可耐受纬度区域的海洋鱼类，其分布范围向极地偏移。主流理论认为，鱼类的最高热极限受低氧与海洋酸化的约束。然而，部分广温性鱼类（eurythermal fish species）并不遵循该理论，它们在低氧环境下仍可维持自身的最高热极限。本研究旨在探明狭温性鱼类（stenothermal species）是否同样符合这一规律。我们以3种珊瑚礁鱼类为研究对象，测试了低氧对其最高热极限的影响，该极限以临界热最大值（critical thermal maximum，CTmax）进行量化。其中，我们还针对其中1个物种，量化了低氧对其供氧能力的影响，该能力以有氧范围（aerobic scope，AS）为衡量指标。针对该物种，我们还测试了高浓度CO₂（模拟海洋酸化）对CTmax低氧敏感性的影响。研究发现，渐进性低氧至约35 mmHg时，临界热最大值（CTmax）并未受到影响，尽管存在显著的低氧诱导……