Patterns of Ecosystem Function and Trophic Status in Well-mixed Subtropical Estuaries Undergoing Anthropogenic Modification

该项目的长期目标是了解温暖，混合良好，亚热带河口如何改变浮游生物群落结构，功能和净生态系统代谢，以应对不断增加的人为营养负荷和自然环境强迫。该方法是继续一个独特的，长期的（19年），时间密集的（采样每周两次）记录在斯基德韦河河口（格鲁吉亚，美国）的水文，营养物质，浮游生物和微生物群落，溶解氧，颗粒物的重要的生物和非生物成分。迄今为止的记录记录表明，从细菌到桡足类的整个食物网的文化富营养化造成的变化;独立收集的证据表明，鳍和贝类的商业捕捞量大幅下降。普遍接受的概念模型和有限的地方证据支持的概念，凝胶捕食者可能受益于增强微生物食物网和减少来自脊椎动物和无脊椎动物的竞争。这些数据将用于评估河口对人类日益占据海岸的副产品以及自然现象中的慢性（长期变暖、海平面上升、长期干旱或潮湿期）和随机（热带风暴）模式的生物和化学反应以及可能的恢复。要解决的问题分为两个基本类别：（a）浮游生物群落（个体分类群和整体特性）在结构和功能上如何对富营养化的早期阶段作出反应，包括所有主要无机和有机营养物的浓度和比例的变化，以及（B）这种变化是否符合河口生态系统的公认生态理论？工作假设是，营养负荷的变化改变了浮游植物，细菌和相关的微生物群落之间的竞争平衡，从而影响更高的营养水平。一个主要的推论是，较低层次的食物网结构的变化正在推动从好氧向缺氧条件的长期转变，即从自养向净异养转变。这些较低的氧气浓度可能会促进凝胶状捕食者群落的发展，以填补鳍和贝类减少所造成的空白。本研究的目的是提供合理的科学数据的历史和当代模式的浮游生物群落结构，生态系统功能，环境变量的关系，包括溶解氧的趋势，以及定量的基础，以评估有关河口生态系统的基本生态假设。更广泛的影响包括一个积极的外展计划，该计划将利用科学成果改善科学教师和课堂教育，并增加非裔美国人和其他少数民族在水产科学中的代表性。这些项目组成部分充分纳入拟议的研究活动，将促进社区认识人口发展、环境质量、生态系统运作和资源养护之间的联系。

The long-term goal of this project is to understand how warm, well-mixed, subtropical estuaries vary their plankton community structure, function, and net ecosystem metabolism in response to increasing anthropogenic nutrient loading and natural environmental forcing. The approach is to continue a unique, long-term (19 years), temporally intensive (sampling twice per week) record in the Skidaway River estuary (Georgia, USA) of hydrography, nutrients, plankton and microbial communities, dissolved oxygen, and important living and non-living components of particulate matter. The record to date documents changes caused by cultural eutrophication throughout the food web from bacteria to copepods; independently collected evidence shows major declines in commercial catches of fin- and shellfish. Commonly accepted conceptual models and limited local evidence support the notion that gelatinous predators may benefit from the enhanced microbial food web and from decreased competition from vertebrates and invertebrates. These data will be used to evaluate estuarine biological and chemical responses to, and potential recovery from, the by-products of increasing human occupation of the coast, as well as chronic (long-term warming, rising sea level, extended drought or wet periods) and stochastic (tropical storms) patterns in natural phenomena. Questions to be addressed fall into two basic categories: (a) how do plankton communities (individual taxa and bulk properties) respond in structure and function to early stages of eutrophication that include changes in concentrations and ratios of all major inorganic and organic nutrients, and (b) are such changes consonant with accepted ecological theory for estuarine ecosystems?The working hypothesis is that changes in nutrient loading have altered the competitive balance among phytoplankton, bacteria, and associated microbial communities, thus impacting higher trophic levels. A major corollary is that changes in food web structure at the lower levels are driving a long-term shift from oxic towards hypoxic conditions, i.e. from autotrophy to net heterotrophy. These lower oxygen concentrations may facilitate the development of gelatinous predators communities to fill the void caused by declines in fin- and shellfish. This study aims to provide sound scientific data on historic and contemporary patterns in plankton community structure, ecosystem function, and relationships to environmental variables, including trends in dissolved oxygen, as well as the quantitative basis to evaluate basic ecological hypotheses regarding estuarine ecosystems. Broader impacts include an active outreach program, which will use the scientific results to improve science teacher and classroom education, as well as to increase the representation of African Americans and other minorities in aquatic sciences. These project components, fully integrated into the proposed research activities, will facilitate community awareness of linkages between population development, environmental quality, ecosystem operation, and resource conservation.