Exploring ecological surprises by multiple stressors of aquatic food webs

我的研究计划的主要目标是发现水生食物网络对全球变化的生态驱动因素。定义全球变化的多个与人类有关的应激源往往对食物网施加复杂的非相加影响，因此不容易根据单一应激源的已知影响总和进行预测。因此，极端气候变化与其他压力因素一起，往往会产生令人震惊的“生态惊喜”。我已经开发了一个影响多种营养对多种应激源反应的生态机制的概念模型。该模型基于三个操作假设：1)应激源对顶级捕食者的协同影响比对植物更显著，因为动物对快速环境变化的耐受性较差，2)比顶级捕食者更能容忍的植物物种能够更容易地在压力下定居生态系统，并在功能上补偿灭绝的物种，因此，3)顶级捕食者、草食动物和植物之间的耐受性差异导致它们之间的相互作用(如捕食和食草)在应激生态系统中发生了深刻的改变。我的研究小组通过在加拿大落基山脉天然无鱼的高山湖泊中进行实验来检验这些假设，这些湖泊越来越多地受到极端气候事件、外来入侵物种和空气污染的影响。因此，这些高度敏感、物种稀少的生态系统是研究多种应激源对营养复杂性的影响的绝佳场所。我们通过使用潜水式温室中胚层将整个食物网、单个营养组及其相互作用顺序地暴露在夏季加热事件和其他应激源中来检查它们的反应。我们还研究了耐受物种的扩散和定居作为缓冲高山食物网免受快速环境变化影响的一种手段的重要性。我通过比较高山湖泊中暴露在相同应激源组合下的实验食物网和自然形成的食物网来完善和升级我提出的模型。我们的发现将有助于更好地解释为什么我们应该期待未来全球变化带来的意想不到的情况。

The main goal of my research program is to discover ecological drivers of aquatic food-web responses to global change. Multiple human-related stressors that define global change often exert complex non-additive effects on food webs, which cannot therefore be easily predicted based on the sum of known effects by single stressors. Consequently, extreme climate change together with other stressors often generate alarming "ecological surprises." I have developed a conceptual model of the ecological mechanisms affecting multi-trophic responses to multiple stressors. The model is based on three operating hypotheses: 1) stressors exert more pronounced synergistic impacts on top predators than on plants because animals are less tolerant of rapid environmental change, 2) tolerant plant species more than top predators are able to readily colonize stressed ecosystems and functionally compensate for extinct species, and thus, 3) differences in tolerances among top predators, herbivores, and plants result in their interactions (e.g., predation and herbivory) being profoundly altered in stressed ecosystems. My research group tests these hypotheses by conducting experiments in naturally fishless alpine lakes of the Canadian Rockies, which are being increasingly impacted by extreme climate events, introduced invasive species, and air pollution. Therefore, these highly sensitive species-poor ecosystems are excellent venues for investigating the effects of multiple stressors on trophic complexity. We examine the responses of whole food webs, single trophic groups and their interactions by exposing them sequentially to summer heating events and other stressors using submersible greenhouse mesocosms. We also examine the importance of dispersal and colonization by tolerant species as a means of buffering alpine food webs against the impacts of rapid environmental change. I refine and upgrade my proposed model through comparison of experimental and naturally occurring food webs in alpine lakes that are exposed to the same combination of stressors. Our findings will help better explain why we should expect the unexpected from future global change.