A novel approach for evaluating temporal and spatial changes in trophic structure of the mesopelagic eastern Pacific

人为和自然的气候扰动导致物种的种群动态、食物网的结构和功能以及生物地球化学过程的变化。PIs建议对三个主要生态系统进行比较分析，以调查中上层食物网结构的时间变化。智力优势：PIS将使用全球分布的顶端捕食者作为指示物种，调查过去50年来三个主要生态系统：加利福尼亚州洋流、东热带太平洋和秘鲁-洪堡洋流中远洋食物网结构的时间变化。捕食者是抹香鲸，即抹香鲸，PI将使用稳定的碳和氮同位素比率作为栖息地和饮食的指示器。牙齿和皮肤大量组织的同位素值(C和N)以及特定氨基酸(N)将用于两个主要目标：(A)审查抹香鲸营养位置的时间模式(作为中上层营养结构变化的指标)和基线同位素值(作为营养循环的指标)；和(B)使用不同系统的同位素值来确定过去和现在抹香鲸的种群结构，以及种群之间的联系。广泛影响：该项目将由学术界和NOAA/NMFS的研究人员进行，他们具有稳定同位素分析、营养生态学和基于生态系统的受保护物种管理方面的专业知识。因此，这是具有互补技能的科学家和来自不同机构的科学家之间合作的机会，以比较东太平洋生态系统的结构和功能。此外，它代表着学术界和一个负责研究和管理职责的联邦机构之间的合作。该项目将支持博士后学者(Iliana Ruiz-Cooley)、博士生和本科生加强他们的职业生涯和合作机会。投资促进机构预计，他们的研究结果将提供独特的数据，以评估中上层生态系统内部和之间的扰动的影响。这些信息可能会让科学界将气候趋势与顶级捕食者营养位置的变化和营养循环联系起来，从而更有力地了解未来可能对气候变暖的反应。最后，作为首次系统地将化合物特异性稳定同位素分析应用于海洋哺乳动物，该项目将对未来评估濒危海洋哺乳动物的摄食生态、种群结构和动态具有很大的指导意义。因此，这种新颖的方法和独特的历史视角将直接适用于库存评估和管理。

Anthropogenic and natural climatic perturbations drive changes in population dynamics of species, the structure and function of food webs, and biogeochemical processes. The PIs propose a comparative analysis of three major ecosystems to investigate temporal change in the structure of mesopelagic food webs. Intellectual Merit: The PIs will investigate temporal changes in the structure of mesopelagic food webs in three major ecosystems: the California Current, Eastern Tropical Pacific, and the Peru-Humboldt Current over the past 50 years using a globally distributed apex predator as an indicator species. The predator is the sperm whale, Physeter macrocephalus, and the PIs will use stable isotope ratios of carbon and nitrogen as indicators of habitat and diet. Isotope values from bulk tissues of teeth and skin (C and N) as well as specific amino acids (N) will be used to address two primary objectives: (a) examine temporal patterns in the trophic position of sperm whales (as an indicator of changes in mesopelagic trophic structure) and baseline isotopic values (as indicators of nutrient cycling); and (b) use isotopic values, which vary among systems, to define the population structure of sperm whales from past and present times, and connectivity among populations.Broader Impacts: This project will be conducted by researchers from academia and NOAA/NMFS with expertise in stable isotope analysis, trophic ecology, and ecosystem-based management of protected species. As such, it represents an opportunity for collaboration between scientists with complementary skills and from diverse institutions to compare structure and function of ecosystems across the eastern Pacific. Moreover, it represents a collaboration between academia and a federal agency with research and management responsibilities. The project will support a postdoctoral scholar (Iliana Ruiz-Cooley), a Ph.D. student, and undergraduate students to enhance their career and collaborative opportunities. The PIs anticipate that the results of their study will provide unique data to evaluate the effects of perturbations within and among mesopelagic ecosystems. This information may allow the scientific community to relate trends in climate to changes in trophic position of top predators and nutrient cycling, allowing more robust understanding of possible responses to future warming. Finally, as the first systematic applications of compound-specific stable isotope analysis to marine mammals, the project should be highly instructive for future evaluations of the feeding ecology, population structure and dynamics of endangered marine mammals. As such, this novel approach and unique historic perspective will be directly applicable for stock assessment and management.