Patterns of Variability in Alaskan Salmon Populations and Their Ecosystems During the Last Five Centuries

了解长期生物变异的原因和表现仍然是生态系统生态学的一个关键和难以捉摸的目标。 在东北太平洋，长期变化的大气-海洋耦合似乎有组织的生物生产到一系列不同的年代际制度在过去的世纪。 例如，阿拉斯加海流鲑鱼捕捞量的三倍变化与年代际气候制度之间的变化是一致的。尽管鱼类种群动态存在巨大的时间变异性，但我们对控制这一巨大而重要的生态系统中生物生产力的长期气候驱动因素的了解却很薄弱。一个关键的假设提出，东北太平洋生物变化的主要驱动因素涉及泛太平洋，二十年和五十年气候振荡的相互作用。 在20世纪世纪之前的生物生产力的历史记录还没有建立阿拉斯加流域的东北太平洋，他们的缺席是一个主要的障碍，了解在这个生态系统中的生物生产力的时间组织。 在这里，研究人员建议量化的基本模式和幅度的年代际变化的红鲑鱼种群的阿拉斯加电流在过去的500年，以提高我们的理解的时间组织在东北太平洋的关键来源。 这些科学家将利用古生态学来描述东北太平洋阿拉斯加海流域生物变异的长期模式。 具体来说，他们将通过跟踪天然地球化学示踪剂（15 N）的变化来推断红鲑鱼（Oncorhynchus nerka）种群的历史变化，该示踪剂在产卵湖泊的沉积物中积累，与鲑鱼密度成比例。将通过对沉积物进行详细的放射性同位素分析和查明已知年代的火山灰层，来确定沉积序列的高分辨率年代。 现有的35至100年的鲑鱼种群动态，气候条件和湖泊生产的历史记录将使他们能够校准地球化学和生物标志物的沉积年表。 他们还将使用沉积物中的碳稳定同位素和藻类色素化石来量化鲑鱼来源的营养物质对湖泊生产力的影响。他们将使用频谱分析和时域时间序列模型来量化鱼类产量历史变化的频率，持续时间和幅度，以及这些变化如何与古气候条件的独立代理相关。 然后，他们将应用从沉积物和其他现有的古气候记录中开发的时间序列模型来预测下一个世纪东北太平洋生物生产力的未来变化。 这种新的和现有的数据的合成将提供一个高分辨率的，具体的描述，在东北太平洋的阿拉斯加电流域的生物生产力的长期变化。他们将检验这一假设，即这一海洋区域内的生物生产力已被与二十年和十五年气候振荡相关的十年间气候制度同步化。 这些数据将提供调查整个东北太平洋生物生产力与气候振荡的空间和时间耦合所需的信息。特别是，我们的工作将提供所需的数据来测试的假设，即在阿拉斯加和加州目前的东北太平洋域的生物生产力同步响应，但不同步，年代际气候强迫。 综合海洋条件、气候条件和生物生产力的历史和古指标，将把最近世纪的生态系统动态置于比目前更长的时间范围内。这些知识将为调整管理以适应东北太平洋沿海海洋、淡水和河岸生态系统的时间尺度提供科学依据。

Understanding the causes and manifestations of biological variability over long time scales remains a critical and elusive goal for ecosystem ecology. In the Northeast Pacific, long-term variation in atmosphere-ocean coupling appears to have organized biological production into a series of distinct interdecadal regimes during the last century. For instance, up to three-fold changes in salmon fishery catches in the Alaska Current were coindicent with shifts between interdecadal climate regimes. Despite this enormous temporal variability in fish population dynamics, we have only a weak understanding of the long-term climatic drivers that control biological productivity in this vast and important ecosystem. A key hypothesis proposes that the main drivers of biological change in the Northeast Pacific involve the interactive effects of pan-Pacific, bi-decadal and penta-decadal climate oscillations. Historical records of biological productivity prior to the 20th century have not been established for the Alaskan Current domain of the Northeast Pacific; their absence represents a major impediment towards understanding the temporal organization of biological productivity in this ecosystem. Here, the investigators propose to quantify the fundamental modes and magnitude of interdecadal variability in sockeye salmon populations of the Alaska Current during the last 500 years, to improve our understanding of the critical sources of temporal organization in the Northeast Pacific. These scientists will use paleoecology to characterize the long-term patterns of biological variability in the Alaskan Current domain of the Northeast Pacific. Specifically, they will infer historical changes in populations of sockeye salmon (Oncorhynchus nerka) by tracking variation of a natural geochemical tracer (15N) that accumulates in the sediments of spawning lakes in proportion to salmon density. High resolution dating of sedimentary sequences will be accomplished through detailed radio-isotope analyses of sediments and by identifying volcanic ash layers with known ages. Existing 35-to-100 year long historical records of salmon population dynamics, climatic conditions, and lake production will enable them to calibrate sedimentary chronologies of geochemical and biological markers. They will also use carbon stable isotopes and fossil algal pigments from sediments to quantify the impact of salmon-derived nutrients on lake productivity. They will use spectral analysis and temporal domain time-series models to quantify the frequency, duration, and magnitude of historical shifts in fish production, and how these relate to independent proxies of paleoclimatic conditions. They will then apply the time-series models developed from sedimentary and other existing paleoclimate records to forecast future changes in the biological productivity of the Northeast Pacific for the next century. This synthesis of new and existing data will provide a high-resolution, concrete description of the long-term variability in the biological productivity of the Alaska Current domain of the Northeast Pacific. They will test the hypothesis that the biological productivity within this oceanic domain has been synchronized by inter-decadal climate regimes associated with bidecadal and pentadecadal climate oscillations. These data will provide the information needed to investigate the spatial and temporal coupling of biological productivity to climate oscillations throughout the Northeast Pacific. In particular, our work will provide the data needed to test the hypothesis that biological productivity in the Alaska and California current domains of the Northeast Pacific respond synchronously, but out of phase, to interdecadal climatic forcing. The synthesis of historical- and paleo-indicators of oceanic conditions, climatic conditions, and biological productivity will place the recent century of ecosystem dynamics in a substantially longer temporal context than is currently available. This knowledge will provide a scientific basis for adapting management to the time scales relevant to the coastal marine, freshwater and riparian ecosystems of the Northeast Pacific.