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

在沿海海洋，营养丰富的河流或河口水域与营养丰富程度较低的海水混合，形成羽流，这些区域非常富有生产力，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。羽流携带的营养物的数量--以及它们对沿海海洋的影响--也会随季节变化。该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如何变化，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。正在开发一种水运动模型，以预测河流流量、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。横跨沿海海洋中羽状物区域的研究巡航正在收集羽状物中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羽流中的物质如何影响动物和沉积物中的化学反应。通过将这一模型、对底层动物生物量和生物多样性的测量以及营养实验相结合，该项目正在确定河口羽流如何驱动沿海食物网和生产力。更广泛的影响包括通过更好地了解羽流动态、食物网和渔业之间的联系而给自然资源管理带来的好处。博士生、博士后学者和本科生正在接受建模、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)建立伙伴关系，招募暑期实习生进行研究，STEM领域的多样性正在增加。推广活动包括为公众编制适合年龄的教育材料，并在“亲身”或虚拟推广活动中使用这些材料。首要目标是确定与空间和时间动态河口羽流有关的有机物输入和环境条件的大小和反应性如何影响内大陆架底栖动物群落。该项目正在分析有机物沉积的作用，包括不稳定的和难熔的，作为底栖群落结构和沉积物-水生物地球化学通量速率的驱动因素。一种综合的方法结合了水动力模型、现场观测和船上实验，将底栖动物的反应与羽流特征的季节性变化联系起来。具体地说，正在使用校准的水动力模型来确定羽流驱动条件的历史，并量化颗粒在内陆架上的传输和沉积。对固定站网的水柱条件、有机质池以及底栖生物和底栖生物群落组成的调查正在产生对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。这些衡量标准正被用来估计二次生产量，并评估它如何随季节变化。底栖生物的沉积物-水营养通量和特定于有机物的养分同化率(不稳定的、难吸收的)正在利用实验岩心培养进行量化。流体动力羽流重建与观测和实验数据相结合，以验证关于季节和空间上输入的羽流颗粒有机物对海底生物量、生物多样性和次生生产的刺激的假设。正在开发统计模型，这些模型考虑了进食模式、过去暴露于羽流影响、沉积有机物的不稳定性和物理力(例如，温度、盐度、床压力)，以预测海底生物对模拟羽流条件的反应，并有可能更广泛地了解羽流动力学。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.