Collaborative Research: Community Mechanisms for Ecosystem Variability in Castle Lake, California.

该提案旨在评估社区如何 相互作用（捕食，竞争）产生的变化， 一系列全湖食物网期间的生态系统动态 操纵 拟议的工作利用了一项计划， 鱼类放养操作由LTREB赠款资助， 国家科学基金会，以及长期记录 本网站的数据收集。 详细研究资源和 食物网优势成分的捕食关系 将使调查人员能够建立负责 每个热带水平的变化，最终在生态系统中 本身 鱼类种群将通过声学监测， 视频观察以及更传统的渔业 技术，以及丰度，生长，饮食， 招募，以及评估为主要变化的浮游动物程度 在外部，鱼类放养强度被强加。 变化 浮游动物动态（特别是水蚤）也将 利用浮游动物种群生物学技术（卵 比率、出生率和死亡率估计数）以及 食物状况的生理指标（脂质含量）。 PI的 也会评估鳟鱼的摄食能力 解释了观察到的水蚤死亡率。 植食性天敌 将通过测量放牧率来评估关系， 浮游动物占优势的主要藻类类群和确定 原位藻类动力学的变化是否可归因于 放牧的影响 植物资源的关系将是 通过监测藻类营养状况和使用 稀释生物测定法测定种属特异性生长动力学 主要限制营养素。 此外， 外部提供的N与内部提供的N（即，在 食物网）在支持藻类生产力方面的作用 使用15 N同位素技术。 摄食和营养/食物供应在 改变浮游生物动态将在受控环境中进行评估。 通过在大型中型生态系统中的实验来设置。 这些实验 将决定浮游生物的反应：1。的梯度 lanktivory压力，这将括号的强度鳟鱼 四年生长期饲养鱼类所涵盖的食物链 anipulations，和，2.对鳟鱼的因子操纵 lanktivory和NO3负荷设计来模拟组合 高和低的外部营养负荷和高和低的鱼类 丝袜 这些实验也提供了额外的舞台 在其中测试模拟模型的预测， 食物网动态和浮游植物群落结构。 城堡湖食物网的功能群模型和 城堡湖食物网的多物种模型和一个多- 浮游植物群落的物种模型（遵循Powell 和Richerson 1985）将被开发为合成的手段， 在我们的基于机制的 观察和实验计划，并推广 获得的洞察力。 参数和模拟条件将 从特定的实验和长期数据中获得 设置并用于进一步探索 社区进程（捕食，基于资源的竞争）和 生态系统特性（年内和年间的模式） 生产力，NO3和NH 4的作用等）

This proposal is designed to evaluate how community interactions (predation, competition) produce changes in ecosystem dynamics during a series of whole-lake food web manipulations. The work proposed capitalizes on a program of fish stocking manipulations funded by an LTREB grant from the National Science Foundation, as well as on the long-term record of data collection at this site. Detailed study of resource-and predator-relations of the dominant components of the food web will allow the investigators the mechanisms responsible for changes in each tropic level and ultimately in the ecosystem itself. Fish populations will be monitored by acoustics and video observation, as well as by more conventional fisheries techniques, and changes in abundances, growth, diets, recruitment, and degree of plankivory evaluated as major changes in external fish stocking intensity are imposed. Changes in zooplankton dynamics (especially of Daphnia) will also be examines using techniques of zooplankton population biology (egg ratios, estimates of birth and death rates) as well as physiological measures of food status (lipid content). The PI's will also evaluate the degree to which trout planktivory accounts for observed Daphnia mortality. Phytoplankton-predator relationship will be assessed by measuring grazing rates by zooplankton dominants on the major algal taxa and determining whether changes in situ algal dynamics are attributable to grazing impacts. Phytoplankton-resource relations will be evaluated by monitoring algal nutritional conditions and using dilution bioassays to determine species-specific growth kinetics for major limiting nutrients. In addition, the roles of externally-supplied N vs. internally-supplied N (i.e. within the food web) in supporting algal productivity will be evaluated using 15 N isotope techniques. The roles of planktivory and nutrient/food supply in altering plankton dynamics will be assessed in controlled settings by experiments in large mesocosms. These experiments will determine plankton responses to: 1. a gradient of lanktivory pressure which will bracket the intensity of trout redation to be encompassed by the 4-year LTREB fish anipulations, and, 2. a factorial manipulation of trout lanktivory and NO3 loading designed to simulate the combination of high and low external nutrient loading and high and low fish stocking. These experiments also provide additional arenas within which to test the predications of simulations models of food web dynamics and phytoplankton community structure. A functional group model of the Castle Lake food web and a multi-species model of the Castle Lake food web and a multi- species model of the phytoplankton community (following Powell and Richerson 1985) will be developed as means of synthesizing the observations obtained during our mechanism-based observational and experimental program and to generalize the insights obtained. Parameters and simulation conditions will be obtained from specific experiments and from the long-term data set and used to further explore the interactions between community processes (predation, resource-based competition) and ecosystem properties (patterns of inter-and intra-annual productivity, the role of NO3 and NH4, etc.)