Collaborative Research: Kelp forest hydrodynamics: observations of drag and cross-shore exchange on the inner shelf

合作研究：海带森林流体动力学：内陆架阻力和跨岸交换的观测

• 批准号: 2022959
• 负责人: James Leichter
• 金额: $ 79.82万
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-10-01 至 2024-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2022959&HistoricalAwards=false
• 关键词: Collaborative; Research; Kelp; forest; hydrodynamics

Kelp forests are common to many mid-latitude coasts, and they are among the most valuable inner shelf habitats for fisheries, recreation, and possibly biological carbon fixation. This project seeks to quantify the wave-dependent drag forces and associated hydrodynamic mechanisms by which giant kelp mediates flow conditions in inner shelf habitats. The frictional drag generated by individual kelp plants and whole kelp forests strongly influence circulation and transport in coastal habitats. However, at present it is not possible to incorporate these effects into coastal circulation models. High-resolution field measurements will be used to develop parameterizations of drag on a whole kelp forest in the presence of coastal currents, surface waves, and internal waves, that will be suitable for use in inner shelf circulation models. The analysis will seek to quantify the magnitude by which kelp forests affect cross-shore exchange on the inner shelf and to determine the mechanisms that mitigate cross-shore exchange in the presence of kelp so that the findings may be generalized to any kelp forest environment. This is relevant to understanding coastal environmental flows and their interactions with a range of types of aquatic vegetation in both natural systems and for large-scale aquaculture and ecosystem management. Understanding their hydrodynamics is thus important to management of coastal waters, as well as to designing natural restoration areas and potential aquaculture systems. Given the rapid development in high resolution circulation models as decision-analysis tools for coastal zone management, including the potentially large hydrodynamic effects of kelp forests can be an essential prerequisite to producing accurate predictions of inner shelf flows. Thus, one particular focus of the project will be to develop a new model for kelp drag in terms of mean currents and wave velocities incorporating simple measures of kelp configuration and biomass that can be used in coastal circulation models. Given the fundamental roles hydrodynamics play in shaping kelp forest ecology through its effects on biogeochemistry and on the transport of larvae, advancing our understanding of kelp forest hydrodynamics will be of use to a wide range of researchers and resource agencies. Moreover, given the large body of ongoing work focused on the Pt. Loma kelp forest, as well as its fundamental importance to the California coastal ocean due to its large size, the results of this study should be of particular use to local scientists and managers. Accordingly, the data collected will also be archived on SCOOS servers as well as on the NODC database. The project will also support graduate education, post-doctoral professional development, and public outreach.The central theme of the project will be to quantify depth-dependent drag associated with flow imposed on flexible vegetative structures – kelp plants in currents and waves – where the movement of the kelp is both influenced by, and in turn mediates, the overall hydrodynamic conditions. Thus, the research will delineate mechanisms of the complex feedbacks between environmental flows and aquatic vegetation that can span the entire water column. While past studies in the field and in the lab have examined elements of this interaction, e.g. changes in mean flows or wave velocity fields by kelp, this study will provide a holistic view of kelp forest hydrodynamics particularly including motion of the kelp. Whereas, in previous field studies kelp drag has always been estimated in ad hoc ways, here it will be measured directly. Quantitative analysis of field observations will test three key hypotheses: (1) Movement of the plants in the presence of waves and sheltering effects that develop when kelp-plant density is sufficiently high are O(1) determinants of mean drag. This hypothesis implies that drag of a whole kelp forest is not a simple linear function of the number of individual kelp plants, but depends on interactions between scale and spacing of individual drag elements and their movement in imposed flows. (2) Wave-current interactions and frequency dependent radiation stress alter the flow field in and around kelp forests. These flow effects along with damping of high frequency internal waves and internal tides and increased diurnal thermal stratification imply that (3a) the presence of a kelp forest can locally enhance cross-shore exchange between the kelp forest and the offshore ocean environment and (3b) a kelp forest acts as a partial barrier that reduces transport between the offshore region and the very near shore region inshore of the kelp. The latter hypothesis predicts the presence of kelp forests can have important consequences for altering circulation and residence time near shore.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.

海带森林对于许多中纬度大衣都是常见的，它们是渔业，娱乐和可能的生物碳固定的最有价值的内书架栖息地之一。该项目旨在量化波浪依赖性的阻力和相关的流体动力机制，通过这些阻力机制，巨型海带介导了内架栖息地中的流动条件。单个海带植物和整个海带森林产生的摩擦阻力强烈影响沿海栖息地的循环和运输。但是，目前不可能将这些影响纳入沿海圆模型。高分辨率场测量将用于在存在沿海电流，表面波和内部波的情况下在整个海带森林上开发阻力的参数，这些参数适用于内部架子圆模型。该分析将旨在量化海带森林影响内架上跨岸交换的大小，并确定在海带存在下减轻跨岸交换的机制，以便发现发现可能被推广到任何海带森林环境。这与了解沿海环境流及其与自然系统和大规模水产养殖和生态系统管理中的一系列水生植被的相互作用有关。因此，了解其流体动力学对于沿海水域的管理以及设计自然恢复区和潜在的水产养殖系统至关重要。鉴于高分辨率循环模型的快速发展是沿海地区管理的决策分析工具，包括海带森林的潜在大型流体动力效应可能是对内部架子流进行准确预测的必要先决条件。该项目的一个特别重点将是开发一种新的模型，以平均电流和波速速度，结合了可用于沿海循环模型中的海带构型和生物量的简单测量。鉴于流体动力学在塑造海带森林生态学方面发挥了基本作用，其对生物地球化学和幼虫的运输的影响，我们对海带森林流体动力学的理解将对广泛的研究人员和资源机构有用。此外，考虑到大量正在进行的工作集中在PT上。洛马·海尔普（Loma Kelp）森林，以及由于其较大的尺寸而对加利福尼亚沿海海洋的根本重要性，这项研究的结果应特别适合当地科学家和经理。根据每个，收集的数据还将在SCOOS服务器以及NODC数据库上存档。该项目还将支持研究生教育，博士后专业发展和公共宣传。该项目的中心主题是量化与柔性营养结构所施加的流量相关的深度依赖性阻力 - 潮流和波浪中的海带植物 - 海带的运动既受海kelp的运动，既受到旋转的影响，又会导致整体流体动力学条件。这是该研究将描述可以跨越整个水柱的环境流和水生植被之间复杂反馈的机制。虽然过去在现场和实验室的研究已经检查了这种相互作用的要素，例如海带的平均流量或波速速度场的变化，这项研究将提供海带森林流体动力学的整体视野，尤其是包括海带运动的运动。尽管在先前的现场研究中，海带阻力始终以临时方式估算，但在这里将直接测量。现场观察的定量分析将检验三个关键的假设：（1）在存在海带植物密度足够高的波浪和遮蔽作用的情况下，植物的运动是O（1）平均阻力的确定剂。该假设意味着整个海带森林的拖曳不是单个海带植物数量的简单线性函数，而是取决于尺度和单个阻力元件间距之间的相互作用及其在强加的流中的运动。 （2）波流相互作用和频率依赖性辐射应力改变海带森林内外的流场。这些流动效应以及高频内波和内部潮汐的阻尼以及增加不同的热分层意味着（3a）海带森林的存在可以局部增强海带森林与海上海洋环境之间的跨岸交换，而（3B）海带森林的部分障碍可以减少在离岸地区和近乎近乎近乎近乎近地区和岸边的近海地区之间的运输，并在岸边的山岸上insephore inse ins ins inse ins inse ins ins ins inse kel kel kel kel kel kel kel kel kel kel kel kel kel kel。后者的假设预测海带森林的存在可能会对改变岸边的循环和停留时间产生重要的后果。该奖项反映了NSF的法定任务，并通过使用基金会的知识分子优点和更广泛的影响审查标准来评估被认为是宝贵的支持。

项目成果

Persistence of southern California giant kelp beds and alongshore variation in nutrient exposure driven by seasonal upwelling and internal waves

南加州巨型海带床的持续存在以及季节性上升流和内波驱动的沿岸营养物暴露变化

• DOI: 10.3389/fmars.2023.1007789
• 发表时间: 2023
• 期刊: Frontiers in Marine Science
• 影响因子: 3.7
• 作者: Leichter, James J.;Ladah, Lydia B.;Parnell, P. Ed;Stokes, M. Dale;Costa, Matthew T.;Fumo, James;Dayton, Paul K.
• 通讯作者: Dayton, Paul K.