Collaborative Research: Diel physiological rhythms in a tropical oceanic copepod

浮游动物和鱼类在浅水和深水沃茨之间跨越数百米的每日垂直迁移（DMV）是远洋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，因为它将大部分固定碳和氮（估计占全球有机输出总量的15%至40%）从地表直接移动到深处，在那里它为中层水食物链提供食物，并将营养素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知之甚少。新的观察表明，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变化，除非基于温度和氧气可用性的变化。然而，速率也受到摄食，游泳行为和潜在昼夜节律周期的差异的影响。该项目的目标是通过详细说明浮游动物生理过程的每日变化，提高科学家理解和预测浮游动物对海洋中碳和氮移动的贡献的能力。通过在每日时间序列中产生一组呼吸和排泄测量值，同时收集大量垂直迁移物种的基因和蛋白质表达模式，研究人员将提供前所未有的预测性见解，了解环境变化如何影响浮游动物对地球化学通量的贡献。该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，重点是海洋的节奏。该单元最初将在百慕大海洋科学研究所夏令营学生中试行，然后通过百慕大海洋科学研究所探索者方案、百慕大海洋科学研究所网站上的教师资源网页传播，并在同行评审的教育期刊上发表，该项目将描述一种模式浮游动物物种-丰富的亚热带桡足类Pleuromamma xiphias-的日常生理节律和DVM的代谢后果。通量过程（耗氧量、二氧化碳产生量、铵产生量和粪粒产生量）将使用测试温度、进食和昼夜节律周期影响的定向实验进行询问。将使用转录组学和蛋白质组学分析进一步检查昼夜节律循环。这些实验将涉及在6小时的时间间隔在昼夜迁移的过程中，使用一套完整的分子和有机体指标的现场样品。结合有机体，转录组学和蛋白质组学的配置文件将提供代谢途径和相关的通量产品的变化与特定的环境变量（食物，光周期，温度）的理解。代谢率的昼夜变化也将评估跨季节和物种使用其他重要的迁徙群体（翼足类，磷虾类，另一桡足类）。然后，代谢数据将与从存档的深度分层拖曳中获得的丰度估计值结合起来，以便按社区一级的模式进行缩放，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善我们的通量估计，并提供各种环境变量如何影响产生碳和氮通量的潜在生理途径的预测洞察力。该奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

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.