Dynamic Stability and Particle Transformations: Tracing Pathways of Production in Estuarine Turbidity Maxima

该项目需要对控制河口最大浑浊度(ETMS)的复杂过程的结构、动力学和生产力进行跨学科研究。由Ed Houde博士领导的这项研究建立在切萨皮克湾最大浑浊度(BITMAX)计划中生物-物理相互作用的广泛结果基础上。ETM是位于淡水/咸水界面附近沿海平原河口头部的物理特征。它们捕获沉积物、碎屑、浮游动物和鱼类早期生命阶段，增强次生生产力，并对滨水鱼类的招募进行控制。BITMAX项目大大提高了对ETM结构和动态的基本知识，但也确定了在理解本提案中涉及的过程和机制方面的关键差距。新的研究目标是定义和评估在ETMS中促进二次生产的过程和机制。在BITMAX中，ETM被确定为一个动态稳定的区域，在那里，物理和生物的恢复力调节ETM生态系统，并周期性地加强营养转移。人们认为，促进ETM动态稳定性的机制与颗粒转化和水柱层化密切相关，后者导致可预测的颗粒输送、捕获、营养丰富和从微生物到浮游动物到鱼类的营养转移。这项研究将解决四个假设：1)颗粒聚集促进ETM中营养颗粒的形成和保留，2)附着在颗粒上的细菌丰富了桡足类食物的营养价值，将微生物环路转变为微生物分流，3)丰富的食物和稳定的层积提高了桡足类和鱼类幼体的摄食条件和产量，以及4)关键ETM物种的生活史策略被调整，以利用ETM循环模式的事件尺度变化(脉冲)。综合研究计划将在切萨皮克湾上游的ETM区域通过全面和协调的野外、实验室和数值模拟实验进行。拟议的研究将扩大有关河口过程的物理和生物学科的知识。研究结果将通过加深对分层潮汐湍流、富营养化环境中颗粒聚集动力学和ETM颗粒捕获的理解，促进对河口物理海洋学和沉积物输运的了解。ETM是世界各地沿海平原河口的高生产力地区。它们是重要经济鱼类的关键育苗区。相互竞争的人类利益通过淡水分流、大坝建设、过量营养物质负荷、河道疏浚和渔业捕捞，影响ETM的物理和/或生物特征。该项目有很强的教育和宣传部分。研究生和本科生将在一个多学科研究计划中接受现场、实验室和建模技术方面的培训。一名教师研究员将获得与科学家合作并将研究成果转化为教案的经验。除了直接培养学生的科学生涯外，研究成果还将通过与切萨皮克湾计划中的资源经理的频繁互动来传播，以确保有效地传达社会效益。

This project entails interdisciplinary research on the complex processes controlling structure, dynamics, and productivity of Estuarine Turbidity Maxima (ETMs). Led by Dr. Ed Houde, it builds on extensive results of the Bio-physical Interactions in the Turbidity Maximum (BITMAX) program in the Chesapeake Bay. ETMs are physical features located at the heads of coastal plain estuaries near the freshwater/saltwater interface. They trap sediment, detritus, zooplankton and fish early-life stages, enhance secondary production, and exercise control over recruitments of anadromous fish. The BITMAX project substantially advanced fundamental knowledge of ETM structure and dynamics, but also identified critical gaps in understanding processes and mechanisms that are addressed in this proposal. The new research objectives are to define and evaluate processes and mechanisms promoting secondary production in ETMs. In BITMAX, the ETM was identified as a region of dynamic stability where restoring forces, both physical and biological, modulate the ETM ecosystem and periodically enhance trophic transfer. It is proposed that mechanisms promoting dynamic stability in ETMs are strongly associated with particle transformations and water column stratification that lead to predictable particle delivery, entrapment, nutritional enrichment, and trophic transfer from microbes to zooplankton to fish. The research will address four hypotheses: 1) particle aggregation promotes formation and retention of nutritious particles in the ETM, 2) particle attached bacteria enrich the nutritional value of food for copepods, transforming the microbial loop into a microbial shunt, 3) abundant food and stable stratification enhance the feeding conditions and production of copepods and fish larvae, and 4) life-history strategies of key ETM species are adapted to take advantage of event-scale changes (pulses) in ETM circulation patterns. The integrated research program will be conducted through comprehensive and coordinated field, laboratory, and numerical modeling experiments in the ETM region of upper Chesapeake Bay. The proposed research will expand knowledge of estuarine processes in physical and biological disciplines. Results will advance knowledge of estuarine physical oceanography and sediment transport by improving understanding of stratified tidal turbulence, particle aggregation dynamics in eutrophic environments, and ETM particle trapping. ETMs are highly productive regions in coastal-plain estuaries throughout the world. They serve as critical nursery areas for economically important fishes. Competing human interests impact physical and/or biological characteristics of the ETM via freshwater diversion, dam construction, excessive nutrient loading, channel dredging, and fisheries harvests. This project has strong education and outreach components. Graduate and undergraduate students will be trained in field, lab and modeling techniques in a multidisciplinary research program. A teacher Fellow will gain experience working with scientists and translating research results into lesson plans. In addition to directly fostering scientific careers of students, research results will be disseminated through frequent interactions with resource managers in the Chesapeake Bay Program to ensure that societal benefits are communicated effectively.