Department of Biology, University of North Carolina at Charlotte, Charlotte, NC 28223, USA.
Integr Comp Biol. 2013 Oct;53(4):597-608. doi: 10.1093/icb/ict028. Epub 2013 Apr 24.
Integrating the effects of multiple stressors and predicting their consequences for the species' survival and distribution is an important problem in ecological physiology. This review applies the concept of energy-limited tolerance to stress to develop bioenergetic markers that can assist in integrating the effects of multiple stressors and distinguishing between the moderate stress compatible with long-term survival of populations and bioenergetically unsustainable extreme stress. These markers reflect the progressive decline of the aerobic scope of an organism (defined as the fraction of the energy flux and metabolic power supporting this flux available after the basal maintenance costs of an organism are met) with increasing levels of the environmental stress. During the exposure to moderate stress (i.e., in the pejus range of the environmental conditions), the aerobic scope is positive but reduced compared with the optimum conditions. The reduction of the metabolic scope can be due to the (1) elevated costs of basal metabolism, (2) activation of the mechanisms for protection and damage repair, (3) reduced assimilation of food, and/or (4) stress-induced impacts on the aerobic pathways producing ATP. This leads to suboptimal growth and reproductive rates in the pejus range of environmental conditions and is commonly observed in food-limited and energy-limited wild populations. The tolerance windows of the organisms are delimited by the pessimum range(s) of environmental conditions in which the aerobic scope of the organism disappears (so that all available energy and metabolic capacity are used in support of basal metabolism), energy resources are depleted, and partial anaerobiosis and/or metabolic rate depression set in. The habitats where environmental conditions remain in the pessimum zone long enough to prevent consistent growth and reproduction often coincide with the species' distributional limits. Thus, focus on the bioenergetic effects of environmental stressors and their immediate consequences for fitness provides a suitable framework for integrating physiology and functional ecology and can assist in understanding the driving forces and limitations of environmental adaptation and improving assessment of ecological risk as well as environmental management in field populations facing multiple stressors.
整合多种胁迫因素的影响并预测其对物种生存和分布的后果是生态生理学中的一个重要问题。本综述应用能量限制耐受的概念来开发生物能量标志物，以帮助整合多种胁迫因素的影响，并区分与种群长期生存相容的适度应激和生物能量上不可持续的极端应激。这些标志物反映了生物体有氧范围的逐渐下降（定义为在满足生物体基本维持成本后，支持该通量的能量通量和代谢功率的分数），随着环境胁迫水平的增加而增加。在适度应激（即在环境条件的 pejus 范围内）暴露期间，有氧范围为正值，但与最佳条件相比有所降低。代谢范围的缩小可能是由于以下原因：(1) 基础代谢的成本增加，(2) 保护和损伤修复机制的激活，(3) 食物同化减少，和/或 (4) 应激对产生 ATP 的有氧途径的影响。这导致在环境条件的 pejus 范围内生长和繁殖率不理想，在食物限制和能量限制的野生种群中经常观察到。生物体的耐受窗口由生物体有氧范围消失的环境条件的 pessimum 范围（即所有可用的能量和代谢能力都用于支持基础代谢）来限定，能量资源耗尽，部分无氧和/或代谢率下降。环境条件在 pessimum 区域内持续足够长的时间以防止持续生长和繁殖的栖息地通常与物种的分布限制相吻合。因此，关注环境胁迫因素的生物能量效应及其对适应性的直接影响提供了一个整合生理学和功能生态学的合适框架，并有助于理解环境适应的驱动力和限制因素，并改善对面临多种胁迫因素的野外种群的生态风险评估和环境管理。
