Collaborative research: A Real-time and Rapid Response Observing System for the Study of Physical and Biological Controls on Muddy Seabed Deposition, Reworking and Resuspension

P.I.Friedrichs，Carl(VIMS)提案编号：0536572 Mean Mail Rating：1.6 High/Low：1.0-2.0 Mean Panel Rating：1.6 High/Low：1.0-2.0 PROJECT标题：一个实时和快速的响应观测系统，用于研究泥质海床沉积、返工和再悬浮的物理和生物控制项目摘要海底可擦性和悬浮颗粒特性的控制是限制泥质海岸环境中细颗粒泥沙输送准确预测的两个最大的未知数。这两个参数很难预测，很大程度上是因为生物效应在短的时间和空间尺度上从根本上影响它们，而物理和生物效应迅速相互反馈。这项研究建议将实时远程观测平台放置在海底物理干扰的对比位置，这些干扰的特点是底栖生态、海底特征和悬浮颗粒特性具有强烈的梯度。结合海底和较低水柱的声学和视频成像，将实时确定生物活动、沉积、侵蚀、悬浮沉积物性质和/或河床形态演变的变化，这些变化反过来又触发或以其他方式表明河床可擦除性的变化。使用实时船上勘测的快速反应巡航将跟踪事件，直接测量可擦除性、关键物理和地球化学性质以及生物活性和组装的短时间尺度演变。河床演变、侵蚀和沉积以及水柱过程的开放源码数值模拟将与观测工作相结合，并将从根本上提高细颗粒泥沙输送的可预测性。拟议的研究区利用在约克河口和下切萨皮克湾正在进行的大量实时观测工作，具有与世界各地在全球沉积物和碳循环中发挥重要作用的高能量、高泥沙负荷大陆架的关键特性。在这类系统中，底栖生物活动的性质、悬浮颗粒的性质和相关的生物-物理反馈与不断演变的盐度锋面以及物理扰动中的空间和时间梯度有关。在美国和世界各地的主要河口也普遍存在这种情况。无论在什么地方，细颗粒泥沙输移的预测都关键依赖于对河床可擦除性和颗粒沉降性的控制。这一建议假设，在生物和物理控制的条件下，细粒沉积物的床面可擦除性和悬浮集合体的演变是明显不同的。这一建议预测，随着生物活性的增加，床的可擦除性将会更大，并且随着深度的增加而减少的幅度会更小，但由于小规模的生物结合，悬浮聚集体将变得更大和更强。在物理控制的条件下，可擦除性会随着沉积而突然增加，但由于快速固结，随着时间和深度的增加，可擦除性会下降得更快。在物理优势下，悬浮团聚体/絮体会变得更小更弱，下落速度更小，并且由于剪切破碎导致应力增加，悬浮体/絮体的尺寸会减小。

P.I. Friedrichs, Carl (VIMS) Proposal #: 0536572Mean mail rating: 1.6 high/low: 1.0-2.0Mean panel rating: 1.6 high/low: 1.0-2.0PROJECT TITLE: A real-time and rapid response observing system for the study of physical and biological controls on muddy seabed deposition, reworking and re-suspensionProject SummaryControls on seabed erodability and suspended particle properties are the two largest unknowns limiting accurate prediction of fine sediment transport in muddy coastal environments. These two parameters are difficult to predict in large part because biological effects fundamentally impact them over short temporal and spatial scales, and the physical and biological effects rapidly feedback on each other. This study proposes to place real-time remote observing platforms at locations of contrasting benthic physical disturbance that are characterized by strong gradients in benthic ecology, seabed characteristics and suspended particle properties. A combination of acoustic and video imaging of the seabed and lower water column will, in real time, identify changes in biologic activity, deposition, erosion, suspended sediment properties and/or bedform evolution that, in turn, trigger or otherwise indicate changes in bed erodability. Rapid response cruises employing real-time shipboard surveys will track events, directly measuring the short time-scale evolution of erodability, key physical and geochemical properties, and biological activity and assemblages. Open source numerical modeling of bed evolution, erosion and deposition, and water column processes will be coupled to the observing effort and will fundamentally advance predictability of fine sediment transport. The proposed study area, which leverages significant real-time observing efforts underway in the York River estuary and Lower Chesapeake Bay, has key properties in common with energetic, high sediment load shelves around the world which play essential roles in the global sediment and carbon cycles. In such systems, the nature of benthic biological activity, suspended particle properties and associated biological-physical feedbacks are tied to evolving salinity fronts and spatial and temporal gradients in physical disturbance. This is also commonly the case along major estuaries in the US and worldwide. Regardless of the locale, prediction of fine sediment transport relies critically on understanding controls on bed erodability and particle settling. This proposal hypothesizes that the evolution of bed erodability and suspended aggregates of fine sediment is distinctly different under biologically vs. physically dominated conditions. This proposal predicts that with increased biological activity, bed erodability will be greater and decrease less strongly with depth, but suspended aggregates will be larger and stronger due to small-scale biological binding. Under physically dominated conditions, erodability will increase suddenly with deposition, but decrease more quickly with time and depth due to rapid consolidation. Under physical dominance, suspended aggregates/flocs will be smaller and weaker, have smaller fall velocities, and decrease in size with increased stress due to breakup by shear.