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.

海带森林在许多中纬度海岸很常见，它们是最有价值的内陆架栖息地之一，用于渔业、娱乐和可能的生物固碳。这个项目旨在量化的波浪依赖的阻力和相关的流体动力学机制，巨型海带介导的流动条件在内陆架栖息地。个别海藻植物和整个海藻森林产生的摩擦阻力强烈影响沿海栖息地的循环和运输。然而，目前还不可能将这些影响纳入沿海环流模式。高分辨率的现场测量将用于开发参数化的阻力对整个海带森林的存在下，沿海流，表面波，内波，这将是适合于使用内大陆架环流模型。分析将力求量化巨藻森林影响内大陆架跨岸交换的程度，并确定在巨藻存在下减轻跨岸交换的机制，以便将研究结果推广到任何巨藻森林环境。这对于理解沿海环境流动及其与自然系统中各种水生植被的相互作用以及大规模水产养殖和生态系统管理都具有重要意义。因此，了解它们的水动力学对沿海沃茨的管理以及设计自然恢复区和潜在的水产养殖系统都很重要。鉴于高分辨率环流模型作为沿海区管理的决策分析工具的迅速发展，包括海带森林潜在的巨大流体动力学效应可能是准确预测大陆架内水流的必要先决条件。因此，该项目的一个特别重点将是开发一个新的模式，根据平均海流和波浪速度计算海带阻力，其中包括可用于沿海环流模式的海带结构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中发挥的基本作用，通过其对藻类地球化学和幼虫运输的影响，推进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，鉴于正在进行的大量工作集中在Pt上。洛马海带森林，以及它的根本重要性，加州沿海海洋由于其规模大，这项研究的结果应该是特别有用的当地科学家和管理人员。因此，收集的数据也将在SCOOS服务器和NODC数据库中存档。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植物结构（水流和波浪中的海带植物）上的流动相关的深度相关阻力，其中海带的运动既受整体水动力条件的影响，又反过来介导整体水动力条件。因此，这项研究将描绘环境流动和水生植被之间的复杂反馈机制，可以跨越整个水柱。虽然过去的研究在现场和实验室中已经检查了这种相互作用的元素，例如平均流量或波速度场的变化由海带，这项研究将提供一个整体的海带森林流体动力学，特别是包括运动的海带。然而，在以前的实地研究中，海带阻力总是以特别的方式估计，在这里，它将被直接测量。现场观测的定量分析将测试三个关键假设：（1）在波浪和海藻植物密度足够高时产生的遮蔽效应存在时，植物的运动是O（1）平均阻力的决定因素。这一假设意味着整个海带森林的阻力不是单个海带植物数量的简单线性函数，而是取决于单个阻力元素的尺度和间距之间的相互作用以及它们在施加流中的运动。(2)波流相互作用和频率依赖的辐射应力改变流场和周围的海带森林。这些流动效应沿着高频内波和内潮的阻尼和增加的昼夜热分层意味着（3a）海带森林的存在可以局部地增强海带森林和近海海洋环境之间的跨海岸交换，以及（3b）海带森林充当部分屏障，减少海带的近海区域和非常靠近海岸的区域之间的运输。后一种假设预测，海带森林的存在可能会对改变海岸附近的环流和停留时间产生重要影响。该奖项反映了NSF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。

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.