LTER: Nonlinear transitions in the California Current Coastal Pelagic Ecosystem

该奖项将在加利福尼亚洋流系统的沿海上升流生物群系中创建一个长期生态研究站点。研究将集中在导致不同状态的远洋生态系统之间的时间过渡机制。CalCOFI（加州合作海洋渔业调查）沿海海洋时间序列的观测结果（目前已进入第55个年头）表明，在多个时间尺度上，包括厄尔尼诺、多年代际太平洋年代际涛动和多年代际长期变暖趋势等，外部强迫对远洋生态系统的重要性。这种强迫和生物相互作用的相互作用可导致非线性生态系统响应，这种响应可表示为相对突变。这项工作将评估这种生态系统转变的四种假设机制：？-不同组合的持续反常沿岸平流；原位食物网随着分层和养分供应的改变而变化；-生物跨岸运输和损失/保留的变化；以及捕食压力的改变。加州当前生态系统（CCE） LTER站点将通过一个包含三个主要要素的综合研究计划来解决这些假设：(1)实验过程研究将首先关注原位食物网变化的假设。(2)时间序列研究将利用空间分辨时间序列测量评估替代假设，包括不同近岸位置的高频时间测量、卫星遥感和海上广泛的季度测量计划，这些计划将利用并显著增强CalCOFI时间序列。(3)建模和综合研究将有助于量化观测结果背后的动态；通过数值实验和过程模型为假设检验提供平台；提供一种在空间和时间上动态插值观测的方法；并帮助优化现场项目。拟议的研究区域是LTER站点的理想位置：它具有CalCOFI提供的50年气候背景；它位于生物地理边界区，使其成为气候变化的早期哨兵；在相对较小的地理区域内有明显的空间梯度；它的缺氧盆地为古海洋学研究提供了独特的联系；该地区现有的4-D海洋环流物理模式将使生态系统过渡的耦合生物物理模式的发展取得快速进展。该站点将允许LTER网络将沿海上升流生态系统与其他生物群系在以下方面进行比较：初级生产的模式和控制，选择代表营养结构的种群的时空分布，无机输入和营养物质运动的模式，以及干扰的模式和频率。更广泛的影响：该项目将拥有最先进的信息和数据管理，为LTER合作伙伴、教育工作者、公众和政策制定者提供内部数据服务。一个积极的教育和推广项目将与CA-COSEE和外部合作伙伴合作，让K-12社区参与到这项研究的过程中，并从这项研究中获得理解。他们将跨越学科界限培养本科生、研究生和博士后学者。通过与非正式科学教育组织的合作，他们每年将为数百名K-12学童提供服务，其中包括当地低收入和少数民族学生。教师和学生将参加实地研究并接受海洋科学方面的培训。他们还将协助制定新的学校课程。

This award will create a LTER-Long-Term Ecological Research site in the coastal upwelling biome of the California Current System. The research will focus on mechanisms leading to temporal transitions between different states of the pelagic ecosystem. Observations from the CalCOFI (California Cooperative Oceanic Fisheries Investigations) coastal ocean time series, currently in its 55th year, demonstrate the importance of external forcing of the pelagic ecosystem on multiple time scales, including: El Nino, the multi-decadal Pacific Decadal Oscillation, and a multi-decadal secular warming trend. Interactions of such forcing and biotic interactions can lead to nonlinear ecosystem responses that may be expressed as relatively abrupt transitions. The work will evaluate four hypothesized mechanisms for such ecosystem transitions:?-Sustained, anomalous alongshore advection of different assemblages; -In situ food web changes in response to altered stratification and nutrient supply; -Changes in cross-shore transport and loss/retention of organisms; and-Altered predation pressure. The California Current Ecosystem (CCE) LTER site will address these hypotheses with an integrated research program having three primary elements: (1) Experimental Process Studies will initially focus on the hypothesis of in situ food web changes. (2) Time Series Studies will evaluate alternative hypotheses using space-resolving time series measurements, including high frequency temporal measurements at different nearshore locations, satellite remote sensing, and an extensive quarterly measurement program at sea that will capitalize on and significantly enhance the CalCOFI time series. (3) Modeling and synthesis studies will help quantify the dynamics underlying the observations; provide a platform for hypothesis testing through numerical experiments and process models; provide a means for dynamic interpolation between observations in space and time; and help optimize the field program. The proposed study region is an ideal location for an LTER site: it has 5 decades of climate context provided by CalCOFI; it is in a biogeographic boundary region, making it an early sentinel of climate change; it has pronounced spatial gradients in a relatively small geographic area; its anoxic basins provide a unique connection to paleoceanographic studies; and the extant 4-D physical ocean circulation model of the region will permit rapid advances in the development of coupled bio-physical models of ecosystem transitions. The site will allow the LTER network to compare coastal pelagic upwelling ecosystems with other biomes with respect to: Pattern and control of primary production, Spatial and temporal distribution of populations selected to represent trophic structures, Patterns of inorganic inputs and movements of nutrients, and Patterns and frequency of disturbances. Broader Impacts: The project will have state of the art Information and Data Management to serve data internally, to LTER partners, educators, the general public, and policy makers. An active Education and Outreach program will team scientists with CA-COSEE and external partners to engage the K-12 community in both the process of and the understanding gained from this research. They will train undergraduates, graduate students, and postdoctoral scholars across disciplinary boundaries. Through collaborations with informal science education organizations, they will reach hundreds of K-12 schoolchildren each year, including local low-income and minority students. Teachers and students will participate in field studies and gain training in oceanographic science. They will also assist in the development of new school curricula.