Estuary plumes as drivers of inner continental shelf benthic community structure and function

在沿海海域，营养丰富的河流或河口水域与营养不丰富的海水混合，形成羽状流，这些区域对渔业和营养循环非常重要。由于天气、风和洋流的季节性变化，这些河口羽流的位置和大小是高度动态的。羽流携带的营养物质的数量——以及它们对沿海海洋的影响——也会随季节而变化。这个项目正在研究美国最大的河口切萨皮克湾的羽流在一年中是如何变化的，以及这些变化对大西洋沿岸的食物网和营养循环意味着什么。人们正在开发一种水运动模型，以预测河流、风和水流如何汇聚，从而导致羽流大小、位置和组成的季节性变化。在沿海海洋中横跨羽流区域的研究游船正在收集羽流内的物质以及生活在沉积物下面和上面的动物。与此同时，在船上进行的实验正在调查动物和沉积物中的化学反应是如何受到羽流内物质的影响的。通过结合这个模型、对海底动物生物量和生物多样性的测量以及营养实验，这个项目正在确定河口羽流是如何驱动沿海食物网和生产力的。更广泛的影响包括通过更好地了解羽流动力学、食物网和渔业之间的联系，对自然资源管理的好处。对博士生、博士后和本科生进行建模、实验和实地研究方法的培训。通过与一所社区学院（南马里兰学院）合作，招募暑期实习生进行研究经验，STEM领域的多样性正在增加。外展活动包括为公众开发适合年龄的教育材料，并在“亲自”或虚拟外展活动中使用这些材料。总体目标是确定与空间和时间动态河口羽流相关的有机质输入和环境条件的大小和反应性如何影响内陆大陆架底栖生物群落。该项目正在分析不稳定和不稳定的有机物沉积作为底栖生物群落结构和沉积物-水生物地球化学通量率的驱动因素的作用。一种综合方法将流体动力学建模、实地观察和船上实验结合起来，将底栖生物的反应与羽流特征的季节性变化联系起来。具体来说，一个校准的水动力学模型被用来建立羽流驱动条件的历史，并量化颗粒在内大陆架上的运输和沉积。在固定站网格上对水柱条件、有机物库、底栖生物和外底栖生物群落组成进行调查，产生底栖生物分类和功能组成、生物多样性和生物量的经验测量结果。这些测量被用来估计二次产量，并评估其季节性变化。底栖生物的沉积物-水营养物通量和有机物特定营养物同化率（不稳定的、难降解的）正在使用实验核心孵育进行量化。流体动力学羽流重建与观测和实验数据相结合，以验证有关羽流颗粒有机物输入对底栖生物生物量、生物多样性和次生生产的季节性和空间刺激的假设。目前正在开发统计模型，用于预测底栖生物对模拟羽流条件的反应，这些模型考虑了进食方式、过去受到羽流影响的情况、沉积有机质的不稳定性和物理力（如温度、盐度、床应力），并有可能更广泛地了解羽流动力学。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

In the coastal ocean, nutrient-rich river or estuary waters mix with less-enriched marine waters creating plumes, regions that are very productive and important for fisheries and nutrient cycling. The location and size of these estuary plumes are highly dynamic because of seasonal changes in weather, winds, and ocean currents. The amount of nutrients carried by plumes – and thus their impact on the coastal ocean – also changes seasonally. This project is studying how the plume of the nation’s largest estuary, the Chesapeake Bay, changes over the course of the year and what those changes mean for food webs and nutrient cycles in the coastal Atlantic Ocean. A model of water movements is being developed to predict how river flow, winds, and currents converge to cause seasonal changes in plume size, location, and composition. Research cruises spanning the area of the plume within the coastal ocean are collecting material within the plume as well as the animals living under and on top of the sediments. In parallel, experiments conducted on the ship are investigating how the animals and the chemical reactions in the sediment are affected by materials within the plume. By combining this modelling, measurements of bottom animal biomass and biodiversity, and nutrient experiments, this project is determining how estuarine plumes drive coastal food webs and productivity. Broader impacts include benefits to natural resource management through a better understanding of the linkages between plume dynamics, food webs and fisheries. Doctoral students, a postdoctoral scholar and undergraduate students are being trained in modeling, experimental and field research methods. Increasing diversity in STEM fields is occurring through a partnership with a community college (College of Southern Maryland) to recruit summer interns for research experiences. Outreach activities include the development of age-appropriate educational materials for the public and the use of these materials at ‘in person’ or virtual outreach events.The overarching goal is to determine how the magnitude and reactivity of organic matter inputs and environmental conditions associated with spatially and temporally dynamic estuarine plumes affect inner continental shelf benthic communities. The project is analyzing the role of organic matter deposition, both labile and refractory, as a driver of benthic community structure and sediment-water biogeochemical flux rates. An integrative approach that combines hydrodynamic modelling, field observations and shipboard experiments is linking benthic responses to seasonal changes in plume characteristics. Specifically, a calibrated hydrodynamic model is being used to establish the history of plume-driven conditions and to quantify particle transport and deposition on the inner shelf. A survey of water-column conditions, organic matter pools, and benthic and epibenthic community composition at a fixed station grid are generating empirical measurements of benthic taxonomic and functional composition, biodiversity, and biomass. These measurements are being used to estimate secondary production and assess how it varies seasonally. Sediment-water nutrient fluxes and organic matter-specific nutrient assimilation rates (labile, refractory) by benthos are being quantified using experimental core incubations. Hydrodynamic plume reconstructions are coupled with observational and experimental data to test hypotheses regarding the stimulation of benthic biomass, biodiversity, and secondary production by plume particulate organic matter inputs both seasonally and spatially. Statistical models that account for feeding mode, past exposure to plume influence, lability of deposited organic matter, and physical forces (e.g., temperature, salinity, bed stress) are being developed to predict benthic responses to simulated plume conditions and, potentially, inform understanding of plume dynamics more broadly.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.