LTER: Nonlinear transitions in the California Current Coastal Pelagic Ecosystem

该奖项将在加利福尼亚州当前系统的沿海上升生物群中创建一个LTER-长期生态研究地点。这项研究将侧重于导致远洋生态系统不同状态之间的时间过渡的机制。来自加州合作海洋渔业调查组织(CalCOFI)沿海海洋时间序列的观测表明，海洋生态系统的外部强迫在多个时间尺度上的重要性，包括：厄尔尼诺、多年代际太平洋年代际振荡和多年代际长期变暖趋势。这种强迫作用和生物作用的相互作用可能会导致非线性生态系统反应，这种反应可能表现为相对突然的转变。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、异常的近岸平流；-原地食物网对变化的层化和营养供应的响应；-生物跨岸运输和损失/保留的变化；以及-捕食压力的变化。加州当前生态系统(CCE)LTER网站将通过一个包含三个主要元素的综合研究计划来解决这些假设：(1)实验过程研究最初将专注于就地食物网变化的假设。(2)时间序列研究将使用空间分辨率时间序列测量来评估替代假设，包括不同近岸位置的高频时间测量、卫星遥感以及将利用并显著增强CalCOFI时间序列的广泛的海上季度测量计划。(3)建模和综合研究将有助于量化观测背后的动力学；通过数值实验和过程模型提供假设检验的平台；提供空间和时间观测之间的动态内插的手段；并有助于优化实地方案。拟议的研究区是建立长期热辐射实验场的理想地点：它拥有CalCOFI提供的50年气候背景；它位于生物地理边界区域，使其成为气候变化的早期哨所；它在相对较小的地理区域具有明显的空间梯度；其缺氧盆地为古海洋学研究提供了独特的联系；该区域现有的4维物理海洋环流模型将使生态系统过渡的耦合生物物理模型的开发取得快速进展。该站点将使LTER网络能够在以下方面将沿海浮游上升流生态系统与其他生物群进行比较：初级生产的模式和控制、被选来代表营养结构的种群的时空分布、无机输入和营养物质的移动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、普通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计划将与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和理解中。他们将跨学科培养本科生、研究生和博士后学者。通过与非正式科学教育组织的合作，他们每年将接触到数百名K-12学童，包括当地的低收入和少数民族学生。教师和学生将参加实地考察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.