Minutietal2021_STOT_heatwaves and recovery effects on sea urchin

Heatwaves are increasing in frequency and intensity, with substantial impacts on ecosystems and species which maintain their function. Whether or not species are harmed by heatwave conditions by being pushed beyond their physiological bounds can depend on whether energy replacement is sufficient to enable recovery from acute stress. We exposed an ecologically important sea urchin, Heliocidaris erythrogramma, to experimental marine heatwave scenarios in context with recent summer heat anomalies in moderate (25 °C), and strong heatwave (26 °C) conditions for 10 days, followed by a 10-day recovery period at normal summer temperature (23 °C). Greater heatwave intensity drove higher metabolic rates which were not matched with a concurrent increase in food consumption or faecal production. However, food consumption increased during the post-heatwave recovery period, likely to replenish an energy deficit. Despite this, mortality increased into the recovery period and seemed to be caused by latent effects, manifesting as a decline in health index as individuals progressed from spine and pedicellariae loss, through to loss of tube foot rigor, bald patch disease, culminating in mortality. We show for the first time that the acute thermal stress of heatwaves can have latent physiological effects that cause mortality even when conditions return to normal. Our results show that the negative effects of heatwaves can manifest after relief from stressful conditions and highlight the importance of understanding the latent effects on physiology and health. This understanding will offer insights into the long-term potential for stress recovery following seemingly sublethal effects and whether the restoration of ambient conditions post-heatwave is sufficient to ensure population stability.

热浪的频率和强度正在上升，对维持其功能的生态系统和物种产生了重大影响。物种是否因热浪条件而被推至生理极限而受到损害，取决于能量补充是否足以使它们从急性压力中恢复。本研究将生态学上具有重要意义的海胆 Heliocidaris erythrogramma 暴露于实验性海洋热浪情景中，这些情景与近期夏季的温和热异常（25°C）和强烈热浪（26°C）条件相对应，持续10天，随后在正常夏季温度（23°C）下进行10天的恢复期。更高的热浪强度驱使新陈代谢率上升，但并未伴随着食物消耗或粪便产生的同步增加。然而，在热浪后的恢复期，食物消耗量增加，可能是为了补充能量亏缺。尽管如此，死亡率在恢复期仍然上升，这似乎是由潜在的效应引起的，表现为健康指数的下降，个体从刺和触手的损失，直至管足失去紧张度，秃斑病，最终导致死亡。我们首次证明，热浪的急性热应激可以产生潜在的生理效应，即使在条件恢复正常时也能导致死亡。我们的结果表明，热浪的负面影响可能在压力缓解之后显现，并强调了理解生理和健康潜在效应的重要性。这种理解将为长期压力恢复的潜在可能性提供洞见，以及热浪后环境条件恢复是否足以确保种群稳定性。