Oligotrophic ocean metabolism from underwater glider observations

水生生物的光合作用和呼吸速率调节着有机物质进入海洋内部的流量，这一过程通过隔离大气中的二氧化碳来影响地球的气候，并为生活在黑暗海洋深处的生物提供了所需的大部分能量。最近传感器技术的改进使得通过精确测量由自主水下航行器和浮子收集的海水中溶解氧的浓度来估计光合作用和呼吸作用成为可能，即使在生物活性较低的海洋区域，如亚热带环流中也是如此。该项目使用自主水下航行器分析了7年来在北太平洋收集的数据，以便获得海洋区域代谢率的前所未有的数量估计，该区域代表了最大的海洋生态系统之一。这种新颖的分析有助于限制海洋中产生的氧气量，并提高我们对光合作用和呼吸作用的变化如何影响有机碳流向海底的理解。作为该项目的一部分，夏威夷大学的两名本科生得到了支持和培训。该项目分析了2008年至2014年（1000天的观测）在北太平洋亚热带环流中使用水下滑翔机收集的公开观测数据，包括温度、盐度、溶解氧、叶绿素荧光和光学后向散射。这些分析用于：(i)量化由双氧振荡引起的混合层总初级生产量和呼吸的原位率，并确定它们的短期变率和季节性；（ii）量化净生物产氧量（混合层和较低光带）并确定其季节性；（三）量化年度群落净产量，由此可以推断有机碳进入海洋内部的净生物通量；（iv）通过比较基于氧的代谢率与浮游植物生物量的光学指标（后向散射和叶绿素荧光），评估生物量的时间变化与代谢率变化之间的关系。这项研究将更好地约束海洋在调节地球气候方面的作用，通过提高对驱动覆盖我们地球很大一部分的寡营养海洋代谢率的时间变化机制的理解。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。

Aquatic photosynthesis and respiration rates regulate the flux of organic matter into the ocean’s interior, a process that impacts Earth’s climate by sequestering carbon dioxide from the atmosphere and that provides most of the energy necessary to support the requirements of the organisms inhabiting the dark depths of the ocean. Recent improvements in sensor technology enabled the estimation of photosynthesis and respiration using accurate measurements of the concentration of oxygen dissolved in seawater collected by autonomous underwater vehicles and floats, even in regions of the ocean with low biological activity such as the subtropical gyres. This project is analyzing data collected in the North Pacific ocean during 7 years using autonomous underwater vehicles in order to obtain an unprecedented number of estimates of metabolic rates for a region of the ocean that is representative of one of the largest oceanic ecosystems. This novel analysis helps constrain the amount of oxygen produced in the sea and improves our understanding of how variations in photosynthesis and respiration influence the flux of organic carbon towards the bottom of the ocean. Two undergraduate students from the University of Hawaii are supported and trained as part of this project. This project is analyzing publicly available observations of temperature, salinity, dissolved oxygen, chlorophyll fluorescence, and optical backscatter collected using underwater gliders in the North Pacific Subtropical Gyre between 2008 and 2014 (1,000 days of observations). The analyses are used to: (i) quantify in situ rates of gross primary production and respiration in the mixed layer from diel oxygen oscillations, and determine their short-term variability and seasonality; (ii) quantify the net biological oxygen production (both in the mixed layer and in the lower euphotic zone) and determine its seasonality; (iii) quantify annual net community production, from which one can infer the net biological flux of organic C into the ocean’s interior; and (iv) assess how temporal changes in biomass are linked to changes in metabolic rates by comparing oxygen-based metabolic rates with optical proxies of phytoplankton biomass (backscatter and chlorophyll fluorescence). This investigation will better constrain the role of the ocean in regulating Earth’s climate by improved understanding of the mechanisms driving the temporal variability of metabolic rates in the oligotrophic ocean that covers a large fraction of our planet.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.