Oligotrophic ocean metabolism from underwater glider observations

水生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，这一过程通过将二氧化碳从大气中隔离出来影响地球气候，并提供了支持居住在黑暗海洋深处的生物所需的大部分能量。传感器技术的最新改进使得能够通过准确测量自动水下航行器和浮标收集的海水中溶解的氧浓度来估计光合作用和呼吸作用，即使是在生物活动较少的海洋区域，如亚热带环流。该项目正在使用自动水下航行器分析7年来在北太平洋收集的数据，以便对代表最大海洋生态系统之一的海洋区域的代谢率进行史无前例的估计。这种新颖的分析有助于限制海洋中产生的氧气的数量，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流量的理解。夏威夷大学的两名本科生作为该项目的一部分得到了支持和培训。该项目正在分析2008年至2014年期间在北太平洋亚热带环流使用水下滑翔机收集的关于温度、盐度、溶解氧、叶绿素荧光和光学后向散射的公开观测(1 000天的观测)。分析的目的是：(1)现场量化混合层的初级生产力和呼吸速率，并确定它们的短期变异性和季节性；(2)量化生物氧净生产量(混合层和低真光层)并确定其季节性；(3)量化群落的年净生产量，由此可以推断有机碳进入海洋内部的净生物通量；以及(4)通过比较基于氧气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联系。这项研究将更好地限制海洋在调节地球气候中的作用，因为它可以更好地理解在覆盖地球很大一部分的贫营养化海洋中推动代谢率随时间变化的机制。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。

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.