Collaborative Research: Diel physiological rhythms in a tropical oceanic copepod

浮游动物和鱼类的日垂直迁移（DMV）在浅水和深水之间跨越数百米是中上层生态系统的主要模式。这种迁移对生物地球化学循环产生了影响，因为它将相当一部分固定碳和氮（估计占全球有机出口总量的15%至40%）从地表直接转移到深处，在那里它为中水食物链提供食物，并将营养物质从大气混合中隔离出来。然而，目前对这些通量的估计和预测了解甚少。新的观察结果表明，不确定性的一个来源是由于假设代谢率和过程在一天中不会发生变化，除了基于温度和氧气供应的变化。然而，速率也受到摄食、游泳行为和潜在昼夜周期的差异的影响。该项目的目标是通过详细描述这些生物生理过程的日常变化，提高科学家理解和预测浮游动物对海洋中碳和氮运动的贡献的能力。通过在每天的时间序列中产生一组呼吸和排泄测量，同时收集大量垂直迁移物种的基因和蛋白质表达模式，研究人员将为环境变化如何影响浮游动物对生物地球化学通量的贡献提供前所未有的预测性见解。项目的抽样设计将通过为至少两名本科研究人员提供实践培训机会来促进发现和理解。该项目将通过开发一个教育模块来扩大研究的传播，重点关注海洋的节奏。该模块最初将在百慕大海洋科学研究所（BIOS）夏令营的学生中进行试点，然后通过BIOS Explorer项目和BIOS网站上的教师资源页面进行传播，并在同行评审的教育期刊上发表。本项目将描述一种典型浮游动物物种的日常生理节律和DVM的代谢后果，即丰富的亚热带桡足类鱼胸鱼。通量过程（氧气消耗、二氧化碳生产、铵的生产和粪便颗粒的生产）将通过测试温度、饲养和昼夜周期影响的定向实验进行研究。昼夜循环将进一步使用转录组学和蛋白质组学分析进行检查。这些实验将与在每日迁移过程中每隔6小时采集的现场样本相关，使用一套完整的分子和有机指标。结合生物体、转录组学和蛋白质组学图谱，将有助于了解代谢途径和相关通量产物与特定环境变量（食物、光循环、温度）相关的变化。代谢率的昼夜变化也将通过其他重要的迁徙类群（翼足类、桡足类和另一种桡足类）来评估不同季节和物种之间的差异。然后，代谢数据将与存档的深度分层水体的丰度估计相结合，以允许缩放到群落水平模式，并将用于改进浮游动物对颗粒有机碳、氮和呼吸活性通量的贡献的计算。这项研究的结果将改进我们的通量估计，并为各种环境变量如何影响产生碳和氮通量的潜在生理途径提供预测性见解。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The daily vertical migration (DMV) of zooplankton and fish across hundreds of meters between shallow and deep waters is a predominant pattern in pelagic ecosystems. This migration has consequences for biogeochemical cycling as it moves a substantial portion of fixed carbon and nitrogen (an estimated 15 to 40 % of the total global organic export) from the surface directly to depth where it feeds the midwater food chain and sequesters nutrients away from atmospheric mixing. Estimates and predictions of these fluxes are, however, poorly understood at present. New observations have shown that one source of uncertainty is due to the assumption that metabolic rates and processes do not vary over the course of the day, except based on changes in temperature and oxygen availability. Rates are, however, also driven by differences in feeding, swimming behavior, and underlying circadian cycles. The objective of this project is to improve the ability of scientists to understand and predict zooplankton contributions to the movement of carbon and nitrogen in the ocean by detailing daily changes in physiological processes of these organisms. By producing a set of respiration and excretion measurements over a daily time series, paired with simultaneously collected gene and protein expression patterns for an abundant vertically migratory species, the investigators will provide unprecedented and predictive insight into how changes in the environment affect the contribution of zooplankton to biogeochemical fluxes. The sampling design of the project will advance discovery and understanding by providing hands-on training opportunities to at least two undergraduate researchers. The project will broaden dissemination of the research via development of an educational module, focusing on rhythms in the ocean. The module will initially be piloted with the Bermuda Institute of Ocean Sciences (BIOS) summer camp students and then disseminated through the BIOS Explorer program, the Teacher Resources Page on the BIOS website, and published in a peer-reviewed educational journal.This project will characterize the metabolic consequences of daily physiological rhythms and DVM for a model zooplankton species, the abundant subtropical copepod Pleuromamma xiphias. Flux processes (oxygen consumption, carbon dioxide production, production of ammonium and fecal pellet production) will be interrogated using directed experiments testing the effects of temperature, feeding and circadian cycle. Circadian cycling will further be examined using transcriptomic and proteomic profiling. These experiments will be related to field samples taken at 6-h intervals over the course of the diel migration using an integrated suite of molecular and organismal metrics. Combined organismal, transcriptomic and proteomic profiles will provide an understanding of which metabolic pathways and associated flux products vary in relation to particular environmental variables (food, light cycle, temperature). Diel variation in metabolic rates will also be assessed across seasons and species using other important migratory groups (pteropod, euphausiid, and another copepod). The metabolic data will then be contextualized with abundance estimates from archived depth-stratified tows to allow scaling to community-level patterns and will be used to improve calculations of zooplankton contribution to particulate organic carbon, nitrogen and respiratory active flux. The results of this study will both improve our flux estimates and provide predictive insight into how various environmental variables influence the underlying physiological pathways generating carbon and nitrogen flux.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.