Oxygen and Carbon-based Production and Respiration Rates Across the Pacific Ocean from Profiling Floats

海洋化学和生物在全球碳循环中发挥着重要作用。该项目将描述太平洋生物碳循环的关键组成部分。该团队将使用剖面浮标(配备了几个传感器的自动车辆)来测量氧气和颗粒碳浓度，并估计在所有季节的日常基础上，海洋顶部200米处藻类、细菌和其他生物产生、消耗和损失的碳和氧量。他们还将从科考船上直接测量这些日常数量和其他性质。舰载测量将用于校准浮标测量，并确定光合作用过程中产生的氧气与吸收的二氧化碳的比率，以及呼吸过程中每个有机碳分子利用的氧气的比率在空间中如何变化。人们对这些数量知之甚少，也很少测量，但它们对确定海洋生态系统健康至关重要。除了允许在一个完整的季节周期内进行测量外，浮标数据还将支持对基于卫星的方法的验证，以估计大片海洋地区的碳排放量。总体而言，这些努力解决了更好地了解海洋生产力如何随时间和空间变化以及由于生物过程而将多少碳封存到深海的迫切需要。该项目将包括研究生和本科生在海上的积极参与。研究人员还将作为导师参加夏威夷大学增加研究和合作学习体验联盟(Circle)领导的土著海洋监测伙伴关系计划。该计划邀请当地高中生进行研究，了解他们的健康和海洋健康之间的联系。学生将接受分析浮动车和卫星数据的培训。为了确定全球海洋在时间和空间上的新陈代谢状态，我们必须能够准确地描述初级生产力(PP)和群落呼吸(CR)速率。PP的空间和时间变化知之甚少，因为传统的基于碳和氧的瓶子培养方法所需的努力限制了它们的应用。我们区域和全球模式所依赖的基于卫星的PP估计没有得到很好的验证，而且可能不准确。在初步工作证明，通过自主剖面浮标获得的溶解氧和光学派生颗粒碳的Diel循环可以可靠地估计北太平洋的总生产量(GP)和群落呼吸(CR)速率的基础上，该团队计划使用长期浮式部署来解决整个太平洋盆地的GP和CR的季节性周期，以获得整个真光区的氧和颗粒碳的Diel分辨率测量。之前在亚热带和亚极地北太平洋地区进行的船舶工作发现，生态系统具有一致的生产与呼吸比率，这是意想不到的，因为整个地区的生物量、颗粒碳和叶绿素增加了约10倍，硝酸盐增加了50倍。目前尚不清楚这些比率随着时间的推移可能如何变化，模式是否延伸到赤道和南太平洋，以及溶解有机物生产和呼吸、颗粒输出和浮游植物组成在驱动和/或偏向测量的速率方面可能起到什么作用。总而言之，基于浮动汇率和基于船舶的实验将揭示这些未知因素，为了解流域规模的生态系统功能提供前所未有的视角。该团队预计，在季节性周期中，每个浮动车每年将获得约70个基于氧气和碳的每日速率，这可能会彻底改变我们对生产和呼吸速率如何随时间和空间变化的理解。这项工作将展示一种强大的手段来评估海洋大片区域的基于卫星的PP估计，这是迫切需要的。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Ocean chemistry and biology play an important role in the global carbon cycle. This project will characterize key components of biological carbon cycling in the Pacific Ocean. The team will use profiling floats (autonomous vehicles equipped with several sensors) to measure oxygen and particulate carbon concentrations and estimate the amount of carbon and oxygen produced, consumed, and lost by algae, bacteria, and other organisms in the top 200 meters of the ocean on a day-to-day basis across all seasons. They will also make direct measurements of these daily quantities and other properties from a research ship. The ship-based measurements will be used both to calibrate the float measurements and to determine how the ratio of oxygen produced to carbon dioxide absorbed during photosynthesis, as well as the ratio of oxygen utilized per organic carbon molecule consumed during respiration, vary over space. These quantities are poorly understood and are rarely measured but are critical to determine marine ecosystem health. In addition to allowing measurements over a full seasonal cycle, the float data will support validation of satellite-based methods for estimating carbon production over broad areas of the ocean. Collectively these efforts address the critical need for better understanding how ocean productivity changes over time and space and how much carbon is sequestered to the deep ocean due to biological processes. The project will include active participation of graduate and undergraduate students at sea. The researchers will also participate as mentors in the Indigenous Partnership for Ocean Monitoring led by the Consortium for Increasing Research and Collaborative Learning Experiences, CIRCLE, program at the University of Hawai’i. This program engages local high school students to conduct research to learn about the connection between their health and the health of the ocean. Students will be trained to analyze float and satellite data. In order to determine the metabolic state of global oceans over time and space, we must be able to accurately characterize both primary production (PP) and community respiration (CR) rates. Spatial and temporal variations in PP are poorly known because the effort required for the traditional carbon and oxygen-based bottle incubation methods limits their application. Satellite-based PP estimates on which we rely for regional and global patterns are poorly validated and can be inaccurate. Building upon preliminary work demonstrating that diel cycles of dissolved oxygen and optically-derived particulate carbon obtained via autonomous profiling floats can yield reliable estimates of gross production (GP) and community respiration (CR) rates in the North Pacific Ocean, the team plans to resolve the seasonal cycle of GP and CR across the Pacific basin using long-term float deployments programmed to obtain diel-resolving measurements of oxygen and particulate carbon throughout the euphotic zone. Previous ship-based work in the subtropical and subpolar North Pacific regions found ecosystems marked by consistent production to respiration ratios, which was unexpected given the approximately 10-fold increases in biomass, particulate carbon, and chlorophyll, and 50-fold increase in nitrate across the region. It is unclear how these ratios may vary over time, whether patterns extend to the Equatorial and South Pacific oceans, and what role dissolved organic matter production and respiration, particle export, and phytoplankton composition may have in driving and/or biasing measured rates. Together, float-based rates and ship-based experiments will shed light into those unknowns, allowing an unprecedented view into basin-scale ecosystem functioning. The team expects to obtain approximately 70 oxygen-and carbon-based daily rates per float per year over the seasonal cycle, potentially revolutionizing our understanding of how production and respiration rates vary over time and space. This effort will showcase a powerful means to evaluate satellite-based PP estimates across vast areas of the ocean, which has been critically needed.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.