Global warming is resulting in unprecedented levels of coral mortality due to mass bleaching events and, more recently, marine heatwaves, where rapid increases in seawater temperature cause mortality within days. Here, we compare the response of a ubiquitous scleractinian coral, Stylophora pistillata, from the northern Red Sea to acute (7 h) and chronic (7–11 d) thermal stress events that include temperature treatments of 27°C (i.e., the local maximum monthly mean), 29.5°C, 32°C, and 34.5°C, and assess recovery of the corals following exposure. Overall, S. pistillata exhibited remarkably similar responses to acute and chronic thermal stress, responding primarily to the temperature treatment rather than duration or heating rate. Additionally, corals displayed an exceptionally high thermal tolerance, maintaining their physiological performance and suffering little to no loss of algal symbionts or chlorophyll a up to 32°C, before the host suffered from rapid tissue necrosis and mortality at 34.5°C. While there was some variability in physiological response metrics, photosynthetic efficiency measurements (i.e., maximum quantum yield Fv/Fm) accurately reflected the overall physiological response patterns, with these measurements used to produce the Fv/Fm effective dose (ED₅₀) metric as a proxy for the thermal tolerance of corals. This approach produced similar ED₅₀ values for the acute and chronic experiments (34.47°C vs. 33.81°C), highlighting the potential for acute thermal assays with measurements of Fv/Fm as a systematic and standardized approach to quantitively compare the upper thermal limits of reef-building corals using a portable experimental system.

中文翻译：

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红海珊瑚对急性和慢性热应激暴露的耐受性极高且始终如一

由于大量的漂白事件以及最近的海洋热浪，全球变暖导致珊瑚的死亡率达到空前水平，海水温度的迅速升高导致珊瑚在几天之内死亡。在这里，我们比较了从北部红海到处普遍存在的巩膜珊瑚珊瑚Stylophora pistillata对急性（7 h）和慢性（7-11 d）热应激事件的响应，这些事件包括27°C的温度处理（即局部最大月平均值），29.5°C，32°C和34.5°C，并评估暴露后珊瑚的恢复情况。总体而言，S。pistillata对急性和慢性热应激表现出非常相似的反应，主要是对温度处理而不是持续时间或加热速率的反应。此外，在寄主遭受快速组织坏死和34.5°C的死亡率之前，珊瑚在高达32°C的温度下仍表现出极高的耐热性，保持其生理性能，几乎没有或几乎没有损失藻类共生体或叶绿素a。尽管生理反应指标存在一定差异，但光合作用效率测量值（即最大量子产率Fv / Fm）准确反映了整体生理反应模式，这些测量值用于产生Fv / Fm有效剂量（ED）₅₀）公制作为珊瑚的耐热性的代名词。这种方法在急性和慢性实验（34.47°C对33.81°C）中产生了相似的ED ₅₀值，突显了通过测量Fv / Fm进行急性热分析的潜力，这是一种定量比较比较热上限的系统化和标准化方法便携式实验系统对建造珊瑚礁的珊瑚进行分析。