Collaborative Research: Analysis of Continental Shelf Ecosystems: Food Web Structure and Functional Relations

海洋生态系统的特点是生物成分之间和物理环境内的复杂相互作用。这些系统的复杂性使得它们很难根据观察或模型来理解或解释，这两种方法都受到对自然系统不完整知识的影响。许多科学问题和管理感兴趣的是关于这些系统如何运作以及它们如何随时间变化的广泛而简化的概念的效用。这些概念包括自下而上控制（营养来源和较低营养水平控制生态系统的观点），自上而下控制（营养水平最高的生物控制的观点）和制度转移（由于自然或人为或综合强迫而对系统进行的重大重组）。生物海洋学的一个基本原则是物理过程和种群动态之间的耦合。对这些联系的研究是基于某些简化，特别是强调一个或很少的营养成分。营养网络模型（如ECOPATH）的平行发展代表了从能量转移和捕食者-猎物角度研究更完整的营养群之间关系的努力。然而，生态系统的结构、功能和行为取决于物理环境：混合、平流、水停留时间和季节性，特别是陆架生态系统。这些术语定义了生产、回收和出口率，并设定了底-上层耦合的范围，但它们很少被纳入营养网络模型。显然需要开发便携式的分析方法，以阐明各种生态系统的物理-生物相互作用，并证明它们对所有营养水平的系统生产力和恢复力的影响。然而，同时存在这样的风险，即这些模型变得如此复杂，以至于解开模型动力学的机制和工件很快变得难以处理。一个便携的，耦合的生物物理模型框架的中间营养和物理分辨率是一个潜在的解决方案，将在这个项目中开发。目标是生成足够简单的模型来理解，但又足够复杂以符合实际。因此，预计将包括约5个物理盒子和约20个生态隔间。这些模型将为四种对比鲜明、数据丰富的大陆架生态系统开发。本项目将利用食物网的范围和这四个系统的物理强迫特性来做以下工作。1. 评价以聚合功能群作为适当的营养分辨率水平来研究群落动态的优缺点。2. 比较物理过程和营养网络结构在决定所有营养水平（包括中上层和底栖食物网）的系统生产力、变异性和恢复力方面的相对作用。3. 测试生态系统行为的广泛概念的适用性，如自下而上与自上而下控制群落动态，或突然的政权转移。该项目将通过参与积极的研究，为培养未来的科学家做出贡献。公众将通过开发一个博物馆展览来了解海洋生态系统问题。模型代码将提供给社区以供进一步使用和开发。与NOAA科学家的合作将促进将项目成果应用于实际管理问题。

Marine ecosystems are characterized by complex interactions among biological components and within the physical setting. The complexity of these systems makes them difficult to understand or interpret based on either observations or models, both of which suffer from incomplete knowledge of the natural system. Of interest to many scientific questions and to management is the utility of broad, simplifying concepts about how such systems operate and how they change over time. Among these concepts are bottom-up control (the idea that nutrient sources and lower trophic levels govern the ecosystem), top-down control (the idea that organisms at the highest trophic levels govern), and regime shifts (major restructuring of the system due to natural or anthropogenic, or combined, forcing).A basic tenet of biological oceanography is the coupling between physical processes and population dynamics. The study of these connections has been based on certain simplifications, particularly the emphasis on one, or very few, trophic components. The parallel development of trophic network models (e.g., ECOPATH) represents an effort to study the relationships between a more complete spectrum of trophic groups from an energy transfer and predator-prey perspective. Yet, ecosystem structure, function, and behavior depend on the physical context: mixing, advection, water residence time, and seasonality, especially for shelf ecosystems. These terms define production, recycling, and export rates and set the scope of benthic-pelagic coupling, but they are rarely incorporated into trophic network models. There is clear need to develop portable methods of analysis that can illuminate physical-biological interactions across a wide range of ecosystems and demonstrate their effects on system productivity and resilience at all trophic levels. However, there is a simultaneous risk of such models becoming so complex that untangling the mechanisms and artifacts of model dynamics quickly becomes intractable.A portable, coupled bio-physical model framework of intermediate trophic and physical resolution is a potential solution that will be developed in this project. The goal is to produce models simple enough to understand, but complex enough to be realistic. Thus, about 5 physical boxes and about 20 ecological compartments are expected to be included. The models will be developed for four contrasting, data-rich continental shelf ecosystems. This project will use the range of food webs and physical forcing characteristic of these four systems to do the following. 1. Assess the merits and disadvantages of studying community dynamics in terms of aggregated functional groups as the appropriate level of trophic resolution. 2. Compare the relative roles of physical processes and trophic network structure in determining system productivity, variability, and resilience across all trophic levels, including both pelagic and benthic food webs. 3. Test the applicability of broad concepts of ecosystem behavior such as bottom-up vs. top-down control of community dynamics, or of sudden regime shifts.The project will contribute to the education of future scientists through participation in active research. The public will be informed about ocean ecosystem issues through development of a museum exhibit. Model code will be provided to the community for further use and development. Collaboration with NOAA scientists will foster application of project results to practical management issues.