Does the magnitude of wildlife subsidies influence production, stability, and trophic cascades in a large African river?

该项目将解决马拉河的食物网结构和动态，马拉河是一条跨界河流，为塞伦盖蒂-马拉生态系统提供水源，近100万农村贫困人口，5%的河流流入维多利亚湖和尼罗河流域。马拉河是野生动物唯一的永久水源，因此被认为是塞伦盖蒂的“生命之血”。该建议的重点是营养物添加到河流生态系统的影响，从自然和非常大的输入营养物从剑尾鱼和角马。关键问题是大量和不定期的营养物质输入如何影响河流生态系统的功能？该项目将在马拉河系统进行一系列实验，以解决这一问题。该项目的结果将产生河马的分布和丰度的估计，以及角马溺水事件的位置和规模，这将为塞伦盖蒂-马拉生态系统中河马和角马的管理提供重要信息。河马和角马对肯尼亚和坦桑尼亚的旅游经济极为重要，是值得相当关注的保护物种。与肯尼亚国家博物馆的合作将提供有关马拉河昆虫和鱼类多样性和生物量的重要数据。该项目将培训一名博士后助理，一名研究生和多名本科生，并通过让代表性不足的少数民族本科生参与夏季研究来扩大代表性不足的群体对科学的参与。该项目还将在肯尼亚为美国学生提供实地短期课程。最后，这项研究的结果将通过基于网络的推广活动与全球观众分享，使用实时排放数据，现场照片流，Twitter和博客更新。能量，材料和生物体跨越生态系统边界的运动是许多景观的共同特征。这些空间补贴对社区和生态系统产生了强有力但又多变的影响。空间补贴的规模可能是社区和生态系统一级效应可变性的最重要驱动因素之一。理论表明，低水平的投入稳定食物网，增加社区的持久性，特别是当补充当地生产力的模式，和高水平的投入降低食物网的稳定性，增加营养级联的强度。很少有实证研究涉及补贴规模的影响，这就提出了本提案的核心问题：补贴规模如何影响社区和生态系统进程？马拉河是现存最大的陆地迁徙，约有120万头角马和4,000多头河马。河马，通过排泄和排泄在日常喂养的迁移，和角马，通过尸体输入在大规模溺水，创造了一个自然梯度的补贴投入从上游到下游的马拉河。该项目利用流域范围内的比较，原位比较实验，和小规模的人工流实验，以测试空间补贴的大小如何影响初级和次级生产，营养级联的强度，和食物网的稳定性。该奖项反映了NSF的法定使命，并已被认为是值得支持的，通过评估使用基金会的智力价值和更广泛的影响审查标准。

This project will address food web structure and dynamics in the Mara River, a trans-boundary river that provides water for the Serengeti-Mara Ecosystem, nearly one million rural poor, and 5% of the river flow into Lake Victoria and the Nile Basin. The Mara River is the only permanent source of water for wildlife and is therefore considered the 'life blood' of the Serengeti. This proposal focuses on the effects of nutrient addition to the river ecosystem from natural and exceedingly large inputs of nutrients from hippopotamus and wildebeest. The key question is how do large and irregularly timed nutrient inputs affect the way river ecosystems function? This project will conduct a series of experiments in the Mara river system to address this question. Results of this project will produce estimates of the distribution and abundance of hippos, and the location and magnitude of wildebeest drowning events that will provide important information for the management of hippos and wildebeest in the Serengeti-Mara Ecosystem. Hippos and wildebeest are extremely important to the tourism economy of Kenya and Tanzania and are species of considerable conservation concern. A collaboration with the National Museums of Kenya will provide important data on the diversity and biomass of insects and fish in the Mara River. This project will train a postdoctoral associate, a graduate student, and multiple undergraduate students, and broaden participation of under-represented groups in science by involving underrepresented minority undergraduate students in summer research. This project will also provide field-based short courses in Kenya for US students. Finally, results from this research will be shared with global audiences through web-based outreach initiatives using real-time discharge data, live photo streams from the field, and Twitter and blog updates.The movement of energy, materials, and organisms across ecosystem boundaries is a common feature of many landscapes. These spatial subsidies have strong but variable effects on communities and ecosystems. The magnitude of spatial subsidies may be one of the most important drivers of the variability in community and ecosystem level effects. Theory suggests that low levels of inputs stabilize food webs and increase community persistence, particularly when complementing patterns of local productivity, and high levels of inputs decrease food web stability and increase the strength of trophic cascades. Very little empirical research has addressed the impacts of the magnitude of subsidies, raising the central question of this proposal: how does the magnitude of subsidies influence community and ecosystem processes? The Mara River sustains the largest remaining overland migration of around 1.2 million wildebeest and a population of over 4,000 hippopotamus (hippos). Hippos, through excretion and egestion during daily feeding migrations, and wildebeest, through carcass inputs during mass drownings, create a natural gradient of increasing subsidy inputs from upstream to downstream in the Mara River. This project utilizes basin-wide comparisons, in situ comparative experiments, and small-scale artificial stream experiments to test how the magnitude of spatial subsidies influences primary and secondary production, the strength of trophic cascades, and food web stability.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.