Experiment on the response of the sea star Asterias rubens to heat stress and ocean acidification: experiment 3: A. rubens (fed vs. unfed) oxygen diffusion gradients@en

Robust estimates of marine species vulnerability to ongoing climate change require realistic stressor experiments. Here, we subjected an important coastal predator, the sea star Asterias rubens, to projected warming and ocean acidification over an annual seasonal cycle. Warming and, less so, acidification, had strongly season-specific impacts on animal energy budgets. Specifically, simulated future summer temperatures caused >95% sea star mortality, reduced feeding rate and body mass loss. Additional acute experiments demonstrated that respiratory oxygen flux was preferentially directed to support high summer metabolism at the expense of feeding-related processes. Using 15 years of field temperature data and end of century warming projections, we estimate that potentially lethal summer heat waves will occur in 20% of future years. Our study demonstrates the importance of assessing stress responses along seasonal thermal cycles and the high selective force that future summer heat waves likely can exert on coastal marine animal populations.要精准评估海洋物种对当前气候变化的脆弱性，需开展贴合自然场景的胁迫实验。本研究将重要的沿海捕食者——多棘海盘车（Asterias rubens），置于覆盖年度季节周期的预估增温与海洋酸化环境中进行暴露实验。增温以及程度相对较弱的酸化，对动物能量收支的影响具有显著的季节特异性。具体而言，模拟的未来夏季高温导致超过95%的海盘车死亡，同时降低其摄食率并加剧体重流失。额外开展的急性实验显示，呼吸氧通量优先用于维持夏季的高代谢水平，却以牺牲摄食相关生理过程为代价。结合15年野外温度监测数据与本世纪末增温预估结果，我们估算未来将有20%的年份出现具有致命威胁的夏季热浪。本研究证实了沿季节热周期评估胁迫响应的重要性，以及未来夏季热浪可能对沿海海洋动物种群施加的极强选择压力。