Collaborative Research: Shelfbreak frontal dynamics: mechanisms of upwelling, net community production, and ecological implications

合作研究：货架断裂锋面动力学：上升流机制、净群落生产和生态影响

• 批准号: 1657489
• 负责人: Rachel Stanley
• 金额: $ 10.36万
• 依托单位: Wellesley College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-10-01 至 2021-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1657489&HistoricalAwards=false
• 关键词: Collaborative; Research; Shelfbreak; frontal; dynamics

The continental shelf break of the Middle Atlantic Bight supports a productive and diverse ecosystem. Current paradigms suggest that this productivity is driven by several upwelling mechanisms at the shelf break front. This upwelling supplies nutrients that stimulate primary production by phytoplankton, which in turn leads to enhanced production at higher trophic levels. Although local enhancement of phytoplankton biomass has been observed in some circumstances, such a feature is curiously absent from time-averaged measurements, both from satellites and shipboard sampling. Why would there not be a mean enhancement in phytoplankton biomass as a result of the upwelling? One hypothesis is that grazing by zooplankton prevents accumulation of biomass on seasonal and longer time scales, transferring the excess production to higher trophic levels and thereby contributing to the overall productivity of the ecosystem. However, another possibility is that the net impact of these highly intermittent processes is not adequately represented in long-term means of the observations, because of the relatively low resolution of the in-water measurements and the fact that the frontal enhancement can take place below the depth observable by satellite. The deployment of the Ocean Observatories Initiative (OOI) Pioneer Array south of New England has provided a unique opportunity to test these hypotheses. The combination of moored instrumentation and autonomous underwater vehicles will facilitate observations of the frontal system with unprecedented spatial and temporal resolution. This will provide an ideal four-dimensional (space-time) context in which to conduct a detailed study of frontal dynamics and plankton communities needed to examine mechanisms controlling phytoplankton populations in this frontal system. This project will also: (1) promote teaching, training and learning via participation of graduate and undergraduate students in the research , (2) provide a broad dissemination of information by means of outreach in public fora, printed media, and a video documentary of the field work, and (3) contribute to improving societal well-being and increased economic competitiveness by providing the knowledge needed for science-based stewardship of coastal ecosystems, with particular emphasis on connecting with the fishing industry through the Commercial Fisheries Research Foundation.The investigators will conduct a set of three cruises to obtain cross-shelf sections of physical, chemical, and biological properties within the Pioneer Array. Nutrient distributions will be assayed together with hydrography to detect the signature of frontal upwelling and associated nutrient supply. The investigators expect that enhanced nutrient supply will lead to changes in the phytoplankton assemblage, which will be quantified with conventional flow cytometry, imaging flow cytometry (Imaging FlowCytobot, IFCB), optical imaging (Video Plankton Recorder, VPR), traditional microscopic methods, and pigment analysis. Zooplankton will be measured in size classes ranging from micro- to mesozooplankton with the IFCB and VPR, respectively, and also with microscopic analysis. Biological responses to upwelling will be assessed by measuring rates of primary productivity, zooplankton grazing, and net community production. These observations will be synthesized in the context of a coupled physical-biological model to test the two hypotheses that can potentially explain prior observations: (1) grazer-mediated control and (2) undersampling. Hindcast simulations will also be used to diagnose the relative importance of the various mechanisms of upwelling. The intellectual merit of this effort stems from our interdisciplinary approach, advanced observational techniques, and integrated analysis in the context of a state-of-the-art coupled model. The project will address longstanding questions regarding hydrodynamics and productivity of an important ecosystem, leading to improved understanding of physical-biological interactions in a complex continental shelf regime. Given the importance of frontal systems in the global coastal ocean, it is expected that knowledge gained will have broad applicability beyond the specific region being studied.

大西洋中湾的大陆架断裂带支撑着一个富有成效且多样化的生态系统。当前的范例表明，这种生产力是由陆架断裂前沿的几种上升机制驱动的。这种上升流提供了刺激浮游植物初级生产的营养物质，进而导致更高营养水平的产量增加。尽管在某些情况下观察到浮游植物生物量的局部增强，但奇怪的是，卫星和船上采样的时间平均测量结果却没有这种特征。为什么上升流不会导致浮游植物生物量的平均增加？一种假设是，浮游动物的放牧可以防止生物量在季节性和较长时间尺度上的积累，将过剩的生产转移到更高的营养级，从而提高生态系统的整体生产力。然而，另一种可能性是，由于水下测量的分辨率相对较低，而且锋面增强可能发生在卫星可观测深度以下，因此这些高度间歇性过程的净影响并没有在长期观测中得到充分体现。 在新英格兰南部部署海洋观测计划（OOI）先锋阵列为检验这些假设提供了独特的机会。系泊仪器和自主水下航行器的结合将有助于以前所未有的空间和时间分辨率观测锋面系统。这将提供一个理想的四维（时空）背景，在其中对锋面动力学和浮游生物群落进行详细研究，以检查控制该锋面系统中浮游植物种群的机制。 该项目还将：（1）通过研究生和本科生参与研究来促进教学、培训和学习，（2）通过公共论坛、印刷媒体和实地工作视频纪录片的方式广泛传播信息，以及（3）通过提供沿海生态系统科学管理所需的知识，特别强调与渔业的联系，促进改善社会福祉和提高经济竞争力。 研究人员将通过商业渔业研究基金会进行一系列的三次巡航，以获得先锋阵列内跨大陆架部分的物理、化学和生物特性。营养物分布将与水文学一起进行分析，以检测锋面上升流和相关营养物供应的特征。研究人员预计，营养供应的增强将导致浮游植物组合的变化，这将通过传统流式细胞术、成像流式细胞术（Imaging FlowCytobot，IFCB）、光学成像（Video Plankton Recorder，VPR）、传统显微方法和色素分析来量化。浮游动物将分别使用IFCB和VPR以及微观分析来测量从微型到中型浮游动物的尺寸等级。将通过测量初级生产力、浮游动物放牧和群落净生产率来评估对上升流的生物反应。这些观察结果将在物理-生物耦合模型的背景下进行综合，以测试可能解释先前观察结果的两个假设：（1）放牧介导的控制和（2）欠采样。后报模拟还将用于诊断各种上升流机制的相对重要性。 这项工作的智力价值源于我们的跨学科方法、先进的观察技术以及最先进的耦合模型背景下的综合分析。该项目将解决有关重要生态系统的流体动力学和生产力的长期问题，从而提高对复杂大陆架体系中物理-生物相互作用的理解。鉴于锋面系统在全球沿海海洋中的重要性，预计所获得的知识将在所研究的特定区域之外具有广泛的适用性。

项目成果

A Regional, Early Spring Bloom of Phaeocystis pouchetii on the New England Continental Shelf

• DOI: 10.1029/2020jc016856
• 发表时间: 2021-02
• 期刊: Journal of Geophysical Research: Oceans
• 作者: W. Smith;W. Zhang;Andrew J. Hirzel;R. Stanley;M. G. Meyer;H. Sosik;P. Alatalo;H. Oliver;Z. Sandwith;E. T. Crockford;Emily E. Peacock;Arshi Mehta;D. McGillicuddy