Environmental stress can reshape trophic interactions by excluding predators or rendering prey vulnerable, depending on the relative sensitivity of species to the stressor. Classical models of food web responses to stress predict either complete predator exclusion from stressed areas or complete prey vulnerability if predators are stress tolerant. However, if the consumer response to the stress is individually variable, the result may be a distributive stress model (DSM) whereby predators distribute consumption pressure across a range of prey guilds and their trophic niche is expanded. We test these models in one of the largest hypoxic “Dead Zones” in the world, the northern Gulf of Mexico, by combining geochemical tracers of hypoxia exposure and isotope ratios to assess individual-level trophic responses. Hypoxia-exposed fish occupied niche widths that were 14.8% and 400% larger than their normoxic counterparts in two different years, consistent with variable displacement from benthic to pelagic food webs. The degree of isotopic displacement depended on the magnitude of hypoxia exposure. These results are consistent with the DSM and highlight the need to account for individually variable sublethal effects when predicting community responses to environmental stress.

中文翻译：

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分配压力：个体对缺氧的不同反应扩大了鱼类的营养生态位

环境压力可以通过排除捕食者或使猎物变得脆弱来重塑营养相互作用，具体取决于物种对压力源的相对敏感性。食物网对压力的反应的经典模型预测，如果捕食者能够承受压力，则可以将捕食者完全排除在压力区域之外，或者完全排除猎物。然而，如果消费者对压力的反应是个体可变的，结果可能是一个分配压力模型 (DSM)，其中捕食者在一系列猎物公会中分配消费压力，并扩大它们的营养生态位。我们在世界上最大的缺氧“死区”之一——墨西哥湾北部测试这些模型，通过结合缺氧暴露和同位素比率的地球化学示踪剂来评估个体水平的营养反应。在两个不同的年份，缺氧暴露的鱼占据的生态位宽度比常氧鱼大 14.8% 和 400%，这与从底栖到远洋食物网的可变位移一致。同位素置换的程度取决于缺氧暴露的程度。这些结果与 DSM 一致，并强调在预测社区对环境压力的反应时需要考虑个体可变的亚致死效应。