Stoichiometry in Consumer-Resource Interactions Links Between Nutrient Dynamics and Population Demographics

9421925斯特纳消费者和他们的食物资源，嵌在一个复杂的生态网络中，化学成分并不相同。在将生物质从资源转化为消费者的过程中，发生了相当大的化学重排。化学计量学，或称物质平衡，在重要方面限制了消费者与资源的相互作用。这项拟议的研究将扩展到目前为止在由营养有限的藻类和淡水浮游动物组成的实验系统中所取得的结果。到目前为止的结果表明，限制磷的藻类作为上层营养层的食物比其他生长条件下的藻类要差得多。草食动物的生长与藻类磷含量相关。这个重建项目有几个主要目标。例如，将使用微囊化的磷直接测试浮游动物生长中的矿物质限制。测试将在实验室饲料下进行，使用野外藻类。接下来，这项研究将把迄今仅限于大型水蚤的结果与其他种类的浮游动物进行比较。化学计量学以不同浮游动物消费者的化学含量的形式提供了一种手段，可以先验预测哪些物种将受到食物中磷含量下降的最大影响。在这些研究中，如果磷含量确实是重要的饮食因素，与水蚤相比，淡水桡足类组织中的磷含量较低，因此受到低磷食物的影响应该比水蚤小。这个项目的最后一个主要目标是收集大量关于消费者内部化学计量的数据，并将其发展成动物体内磷平衡的模型，类似于生物能量学模型。将对N：P比例不同的几种浮游动物的体细胞组织、两性卵、休眠卵和MOTS的元素含量进行测量。这些结果将与目前的生物能量学模型进行比较，以了解不同的化学成分如何影响动物在不同食物条件下对能量和其他物质的分配。这项研究代表了一种研究消费者动态和食物网络结构的独特方法。人们对资源分配的化学基础知之甚少。通过重点研究食物基地内的资源供应和组成如何影响消费群体，PI将提供关于水生群落中物种相互作用的有价值的信息。然而，这类信息为总体上理解食物资源和营养的化学成分提供了一个重要的框架。

9421925 Sterner Consumers and their food resources, imbedded in a complex ecological web, do not have identical chemical composition. This, in the conversion of biomass from resources to consumers, considerable chemical rearrangement takes place. Stoichiometry, or mass balance, constrains consumer-resource ilteractions in important ways. The proposed research will extend upon the results so far obtained with an experimental system consisting of nutrient-limited algae and freshwater zooplankton. Results so far indicate that P-limited algae are much inferior to algae from other growth conditions as food for upper trophic levels. Herbivore growth correlates with algal P content. There are several major goals for this renewal project. For one, direct tests for mineral limitation in zooplankton growth will be performed using microencapsulated phosphorus. Tests will be performed under laboratory diets using field algae. Next, the research will compare the results so far limited to Daphnia to other species of zooplankton. Stoichiometry, in the form of the chemical content of different zooplankton consumers, provides a means to make a priori predictions about which species will be most affected by reduced P content in their food. If P content is indeed the important dietary factor in these studies, freshwater copepods, with a low P content in their tissues compared to Daphnia, should be less affected by low P food than Daphnia. A final major goal of this project will be to gather a large amount of data on the internal stoichiometry of the consumer, and develop that into a model of P balance in the animal analogous to bioenergetics models. Elemental contents of somatic tissue, amictic eggs, ephippia (resting eggs), and mots will be measured for several zooplankton species differing in N:P ratio. These results will be compared to current models of bioenergetics to see how differing chemical composition might influence the animal's partitioning of energy and other substances under different food cond itions. %%% This research represents a unique approach to consumer dynamics and food web structure. The chemical basis of resource distribution is poorly known. By focusing on how resource supply and composition within the food base affects the consumer populations, the PI will provide valuable information regarding species interactions in aquatic communities. This kind of information, however, provides an important framework for understanding chemical composition of food resources and nutrition, in general.