Biodiversity, Trophic Structure, and the Stability of Seagrass Ecosystems

生物多样性、营养结构和海草生态系统的稳定性。在全球生物多样性下降的许多后果中，对生态系统结构和功能稳定性的影响引起了一些最强烈的兴趣。在过去的十年里，人们重新关注生物多样性对稳定性的长期争论，草原植物组合和实验室微生物微观世界中几个有影响力的实验支持了它们之间的联系。在全球生物多样性加速丧失和同质化的情况下，这些结果如果是普遍的，显然具有重要意义。然而，生物多样性和稳定性之间的联系在自然的、多层次的食物网络中仍然知之甚少。本研究项目将以鳗草(Zostera Marina)床为模型系统，测试将生态系统稳定性与生物多样性和食物网络结构联系起来的一般假设。通过聚焦于全世界沿海生态系统常见的人为扰动--富营养化、过度捕捞和外来入侵--拟议的实验还将严格测试人们普遍认为的自下而上应激源(富营养化)相对于自上而下应激源的影响及其相互作用在海草生态系统持续全球衰退中的主导地位。以前的研究已经证明了生物多样性和营养相互作用对鳗草生态系统关键特性的重要影响。这个项目将把这项研究扩展到更完整的食物网，更广泛的人为扰动，以及对未被操纵的田地系统中的模式的解释。目标是对对人类具有重大意义的海洋生态系统中的生物多样性、食物网络结构和稳定性之间的联系进行全面、机械性的评估。这种整合以前只在少数土壤微型动物和实验室微生物群落中尝试过。具体目标包括：(1)通过实验测试营养层内生物多样性和食物网结构(营养层的数量和组成，以及它们之间的相互作用强度)对鳗草生态系统结构、功能和稳定性的主要和交互影响。(2)实验测试消费者多样性和食物网结构在缓冲海草生态系统中的作用，以对抗人为富营养化、捕食者清除和入侵的影响。(3)测试实验得出的结论预测自然界未经操纵的海草生态系统结构和动态的能力。本项目将使用一套补充的中观实验、田间实验和实验结果的应用来预测和解释未经操纵的田间系统的模式。测量的生态系统响应变量将包括底栖生物量、群落组成和多样性、大型植物优势、初级和次生生产力以及营养转移。该项目有两个主要的更广泛的影响。首先，对生态稳定的普遍关注具有重要的现实意义，因为人类社会强烈依赖水净化和渔业生产等生态系统服务的可靠性。更具体地说，海草床是全世界重要的经济生态系统，但由于被广泛认为是人为富营养化的原因，海草床正在减少。该项目将在实验上测试富营养化和食物网变化在这种下降中的相对重要性。其次，该项目将培训几名学生，从高中到博士水平，在基础和应用海洋生态学的动态界面上对当前问题进行实验研究。最后，它将与最近启动的几个研究项目协调，解决生物多样性和海洋生态系统功能之间的联系，为综合这一领域的努力做出贡献。

Biodiversity, trophic structure, and the stability of seagrass ecosystems.Of the many consequences of declining global biodiversity, impacts on the stability of ecosystem structure and functioning have generated some of the strongest interest. The last decade has seen renewed attention to the long-debated effects of biodiversity on stability, and several influential experiments in grassland plant assemblages and laboratory microbial microcosms support a link between them. These results, if general, are of clear importance in the face of accelerating loss and homogenization of biodiversity worldwide. Yet proposed links between biodiversity and stability remain poorly understood in natural, multi-level food webs.This research project will use eelgrass (Zostera marina) beds as a model system to test general hypotheses linking ecosystem stability with biodiversity and food web structure. By focusing on anthropogenic perturbations common to coastal ecosystems worldwide-eutrophication, overfishing, and exotic invasion-proposed experiments will also test rigorously the widely assumed dominance of bottom-up stressors (eutrophication) in comparison with the impacts of top-down stressors, and their interactions, in the ongoing global decline of seagrass ecosystems. Previous research has demonstrated important effects of biodiversity and trophic interactions on key properties of eelgrass ecosystems. This project will extend this research to more complete food webs, a wider range of anthropogenic perturbations, and interpretation of patterns in unmanipulated field systems. The goal is a comprehensive, mechanistic evaluation of linkages among biodiversity, food-web structure, and stability in a marine ecosystem of strong significance to humans. Such an integration previously has been attempted only for a few soil microfaunal and laboratory microbial communities. Specific objectives include: (1) Test experimentally the main and interactive effects of within-trophic level biodiversity, and foodweb structure (number and composition of trophic levels, and interaction strengths among them), on eelgrass ecosystem structure, functioning, and stability. (2) Test experimentally the roles of consumer diversity and food-web structure in buffering seagrass ecosystems against effects of anthropogenic eutrophication, predator removal, and invasion. (3) Test the ability of experimentally derived conclusions to predict structure and dynamics of unmanipulated seagrass ecosystems in nature.This project will use a complementary suite of mesocosm experiments, field experiments, and application of experimental results to predict and interpret patterns inunmanipulated field systems. Measured ecosystem response variables will include benthic biomass, community composition and diversity, macrophyte dominance, primary and secondary production, and trophic transfer.This project has two principal broader impacts. First, the general focus on ecological stability is of substantial practical importance because human societies depend strongly on reliability of ecosystem services such as water purification and fisheries production. More specifically, seagrass beds are economically important ecosystems worldwide, but are declining for reasons widely attributed to anthropogenic eutrophication. This project will test experimentally the relative importance of eutrophication and food-web changes in this decline. Second, the project will train several students, from high school through Ph.D. levels, in experimental research on current issues at the dynamic interface of basic and applied marine ecology. Finally, it will coordinate with several recently initiated research projects addressing links between biodiversity and marine ecosystem functioning, contributing to an effort toward synthesis of this field.(edited 15 Jan 04, J. Pawlik)