Department of Animal Science, University of California, Davis, Davis, CA 95616, USA.
J Exp Biol. 2022 Jul 15;225(14). doi: 10.1242/jeb.243729. Epub 2022 Jul 26.
Climate change is forecasted to increase temperature variability and stochasticity. Most of our understanding of thermal physiology of intertidal organisms has come from laboratory experiments that acclimate organisms to submerged conditions and steady-state increases in temperatures. For organisms experiencing the ebb and flow of tides with unpredictable low tide aerial temperatures, the reliability of reported tolerances and thus predicted responses to climate change requires incorporation of environmental complexity into empirical studies. Using the mussel Mytilus californianus, our study examined how stochasticity of the thermal regime influences physiological performance. Mussels were acclimated to either submerged conditions or a tidal cycle that included either predictable, unpredictable or no thermal stress during daytime low tide. Physiological performance was measured through anaerobic metabolism, energy stores and cellular stress mechanisms just before low tide, and cardiac responses during a thermal ramp. Both air exposure and stochasticity of temperature change were important in determining thermal performance. Glycogen content was highest in the mussels from the unpredictable treatment, but there was no difference in the expression of heat shock proteins between thermal treatments, suggesting that mussels prioritise energy reserves to deal with unpredictable low tide conditions. Mussels exposed to fluctuating thermal regimes had lower gill anaerobic metabolism, which could reflect increased metabolic capacity. Our results suggest that although thermal magnitude plays an important role in shaping physiological performance, other key elements of the intertidal environment complexity such as stochasticity, thermal variability and thermal history are also important considerations for determining how species will respond to climate warming.
气候变化预计会增加温度的可变性和随机性。我们对潮间带生物热生理学的大部分理解来自于实验室实验，这些实验使生物适应了淹没条件和稳定的温度升高。对于那些经历潮汐涨落且低潮时空气温度不可预测的生物来说，报告的耐受性的可靠性以及对气候变化的预测反应需要将环境复杂性纳入实证研究中。我们使用贻贝 Mytilus californianus 进行了研究，探讨了热环境的随机性如何影响生理表现。贻贝适应于淹没条件或潮汐周期，其中白天低潮时包括可预测的、不可预测的或无热应激。通过无氧代谢、能量储存和细胞应激机制在低潮前测量生理性能，并在热斜坡期间测量心脏反应。空气暴露和温度变化的随机性对热性能的决定都很重要。在不可预测处理的贻贝中，糖原含量最高，但在热处理之间，热休克蛋白的表达没有差异，这表明贻贝优先考虑能量储备来应对不可预测的低潮条件。暴露于波动热环境中的贻贝具有较低的鳃无氧代谢，这可能反映出代谢能力的提高。我们的结果表明，尽管温度幅度在塑造生理表现方面起着重要作用，但潮汐环境复杂性的其他关键因素，如随机性、温度可变性和温度历史，也是确定物种如何对气候变暖做出反应的重要考虑因素。
