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Cyclic thermal fluctuations can be burden or relief for an ectotherm depending on fluctuations’ average and amplitude
Functional Ecology ( IF 4.6 ) Pub Date : 2021-07-22 , DOI: 10.1111/1365-2435.13889 Jahangir Vajedsamiei 1 , Frank Melzner 1 , Michael Raatz 2 , Sonia Moron 3 , Christian Pansch 4
中文翻译：
取决于波动的平均值和幅度，循环热波动可以是变温的负担或缓解
更新日期：2021-07-22
Functional Ecology ( IF 4.6 ) Pub Date : 2021-07-22 , DOI: 10.1111/1365-2435.13889 Jahangir Vajedsamiei 1 , Frank Melzner 1 , Michael Raatz 2 , Sonia Moron 3 , Christian Pansch 4
Affiliation
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- Predicting the implications of ongoing ocean climate warming demands a better understanding of how short-term thermal variability impacts marine ectotherms, particularly at beyond-optimal average conditions during summer heatwaves.
- Using a globally important model species, the blue mussel Mytilus, in a 5-week-long experiment, we (a) assessed growth performance traits under 12 scenarios, consisting of four thermal averages (18.5, 21, 23.5 and 26℃) imposed as constant or daily fluctuating regimes with amplitudes of 2 or 4℃. Additionally, we conducted a short-term assay using different mussel individuals to (b) test for the species capacity for suppression and recovery of metabolic performance traits (feeding and aerobic respiration) when exposed to a 1-day thermal fluctuation regime (16.8–30.5℃). Using this high-resolution data, we (c) generated short-term thermal metabolic performance curves to predict and explain growth responses observed in the long-term experiment.
- We found that daily high-amplitude thermal cycles (4℃) improved mussel growth when fluctuations were imposed around an extreme average temperature of 26℃, representing end-of-century heatwaves. In contrast, thermal cycles negatively affected mussel growth at a less extreme average temperature of 23.5℃, resembling current peak summer temperature scenarios. These results suggest that fluctuations ameliorate heat stress impacts only at critically high average temperatures. The short-term assay demonstrated that during the warming phase, animals stopped feeding between 24 and 30℃ while gradually suppressing respiration. In the subsequent cooling phase, feeding and respiration partially and fully recovered to pre-heating rates respectively. Furthermore, nonlinear averaging of short-term feeding responses (upscaling) well-predicted longer term growth responses to fluctuations.
- Our findings suggest that fluctuations can be beneficial to or detrimental for the long-term performance of ectothermic animals, depending on the fluctuations' average and amplitude. Furthermore, the observed effects can be linked to fluctuation-mediated metabolic suppression and recovery. In a general framework, we propose various hypothetical scenarios of fluctuation impacts on ectotherm performance considering inter- or intra-species variability in heat sensitivity. Our research highlights the need for studying metabolic performance in relation to cyclic abiotic fluctuations to advance the understanding of climate change impacts on aquatic systems.
中文翻译：
取决于波动的平均值和幅度，循环热波动可以是变温的负担或缓解
- 预测持续海洋气候变暖的影响需要更好地了解短期热变率如何影响海洋变温，特别是在夏季热浪期间超出最佳平均条件的情况下。
- 使用全球重要的模式物种蓝贻贝Mytilus，在为期 5 周的实验中，我们 (a) 评估了 12 种情景下的生长性能特征，包括施加为的四个热平均值（18.5、21、23.5 和 26℃）幅度为 2 或 4℃ 的恒定或每日波动状态。此外，我们使用不同的贻贝个体进行了短期测定，以 (b) 测试物种在暴露于 1 天热波动状态 (16.8-30.5) 时抑制和恢复代谢性能特征（摄食和有氧呼吸）的能力℃）。使用这些高分辨率数据，我们 (c) 生成了短期热代谢性能曲线来预测和解释在长期实验中观察到的生长反应。
- 我们发现，当极端平均温度 26℃（代表世纪末的热浪）出现波动时，每日高振幅热循环 (4℃) 促进了贻贝的生长。相比之下，热循环在不太极端的平均温度 23.5℃ 下对贻贝生长产生负面影响，类似于当前的夏季峰值温度情景。这些结果表明，波动仅在极高的平均温度下才能改善热应激的影响。短期试验表明，在升温阶段，动物在 24 至 30℃之间停止进食，同时逐渐抑制呼吸。在随后的冷却阶段，进食和呼吸分别部分和完全恢复到预热速率。此外，
- 我们的研究结果表明，波动可能对变温动物的长期表现有益或有害，这取决于波动的平均值和幅度。此外，观察到的效果可能与波动介导的代谢抑制和恢复有关。在一般框架中，考虑到热敏感性的种间或种内变异性，我们提出了波动对变温性能影响的各种假设情景。我们的研究强调需要研究与周期性非生物波动相关的代谢性能，以促进对气候变化对水生系统影响的理解。
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