Oceans are undergoing successive heatwaves. Several invertebrate taxa associate with dinoflagellates and are susceptible to bleaching caused by heat stress. Although the impacts of a single bleaching event have been well documented, the consequences of successive events are less understood. We investigated the effects of multiple thermal stress events on juvenile Cassiopea andromeda , while also addressing the roles of symbiont concentration and heterotrophic diet regimen. We exposed medusae with two distinct symbiont concentrations (high and low) and under two feeding frequencies ( Artemia offered daily and every 3 days) to three thermal stress events and at three temperatures (control of 27 °C, and treatments of 30 and 33 °C) while recording proportional changes in chlorophyll- a and jellyfish growth. Results show that 30 and 33 °C were not enough to trigger bleaching and did not affect growth. Symbiont concentration also did not affect growth, but medusae with higher symbiont concentration displayed higher chlorophyll- a loss. Diet regimen had little impact on chlorophyll- a variation, but had a dramatic effect on growth, as medusae fed daily grew, while those fed every 3 days shrank. These findings show that it is not possible to evaluate if C. andromeda becomes more resilient after successive thermal stress episodes, because even 33 °C did not generate enough stress. Therefore, C. andromeda juveniles are thermotolerant and may not serve as a good model for investigations on the resilience of coral reef zooxanthellate fauna to the current climate change predictions. Finally, at this life stage, the symbiotic relationship seems less important for growth than heterotrophy.

中文翻译：

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幼年仙后座 andromeda medusae 对多种热应激事件具有抵抗力

海洋正在经历连续的热浪。几种无脊椎动物分类群与甲藻相关，并且容易受到热应激引起的漂白。尽管单个白化事件的影响已被充分记录下来，但对连续事件的后果却知之甚少。我们研究了多种热应激事件对仙后座幼年的影响，同时还解决了共生体浓度和异养饮食方案的作用。我们将具有两种不同共生体浓度（高和低）和两种喂养频率（每天和每 3 天提供卤虫）的水母暴露于三个热应激事件和三个温度（控制 27°C，处理 30°和 33°） C) 同时记录叶绿素 a 和水母生长的比例变化。结果表明，30°C 和 33°C 不足以引发白化，并且不会影响生长。共生体浓度也不影响生长，但具有较高共生体浓度的水母表现出较高的叶绿素 a 损失。饮食方案对叶绿素-a 变异几乎没有影响，但对生长有显着影响，因为每天喂食的水母会生长，而每 3 天喂食的水母会缩小。这些发现表明，无法评估 C. andromeda 在连续热应力事件后是否变得更有弹性，因为即使 33 °C 也不会产生足够的压力。因此，C. andromeda 幼鱼具有耐热性，可能无法作为研究珊瑚礁虫黄藻动物群对当前气候变化预测的恢复力的良好模型。最后，在这个人生阶段，