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

小行星9421925 消费者和他们的食物资源，嵌入在一个复杂的生态网络，不具有相同的化学成分。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，或称质量平衡，以重要的方式限制了消费者-资源的相互作用。拟议的研究将扩展到迄今为止所获得的结果与实验系统组成的营养有限的藻类和淡水浮游动物。到目前为止的结果表明，磷限制藻类是远远低于藻类从其他生长条件下作为食物的上营养级。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。首先，将使用微胶囊化磷对浮游动物生长中的矿物质限制进行直接测试。试验将在实验室饲料中使用田间藻类进行。下一步，研究将比较目前仅限于水蚤和其他浮游动物的结果。化学计量学，在不同的浮游动物消费者的化学含量的形式，提供了一种手段，使先验预测哪些物种将最受影响的减少磷含量在他们的食物。如果磷含量确实是重要的饮食因素，在这些研究中，淡水桡足类，与低磷含量的组织相比，水蚤，应受低磷食物比水蚤。该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，并将其开发成类似于生物能量学模型的动物P平衡模型。元素含量的体细胞组织，amictic鸡蛋，ephippia（休眠蛋），和MOTS将测量几种浮游动物不同的N：P比例。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的能量和其他物质分配。 这项研究代表了消费者动态和食物网结构的独特方法。对资源分布的化学基础知之甚少。通过关注食物基础内的资源供应和组成如何影响消费群体，PI将提供有关水生群落中物种相互作用的宝贵信息。然而，这类信息为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.