Collaborative Research: High resolution glider observations enable reassessment of export production in the oligotrophic Sargasso Sea

几十年来，在百慕大大西洋时间序列研究（BATS）站点等地点进行的观测和测量对于从根本上了解海洋物理、化学和生物学之间的联系至关重要。然而，在BATS现场，尽管观测历史悠久，但一个谜仍然存在：何时以及如何将足够的氮输送到地表沃茨，以支持观察到的生物生产？ 研究人员将在自主水下滑翔机上使用氧气、硝酸盐和微湍流传感器，在BATS现场连续采样20个月，以解开这个谜团。滑翔机使测量过程成为可能，这些过程的尺度无法通过每月或每两周从船上取样来捕获。然而，BATS计划的定期采样对该项目仍然是必不可少的，因为它为滑翔机传感器的校准和验证提供了机会，并为滑翔机的部署和回收提供了船舶支持。该项目还将利用来自BIOS-SCOPE项目的现有私人资金，BIOS-SCOPE项目是BATS的一个多机构微生物海洋生物地球化学倡议，将为滑翔机操作提供部分支持。研究人员每年将招募至少两名NSF本科生研究经验（REU）学生，并将项目主题和数据纳入各自机构的教育计划。该项目将应用新技术来解决几个因素，这些因素被认为使马尾藻海的硝酸盐输送和颗粒有机碳（POC）出口被严重低估。高分辨率滑翔机为基础的观测将被用来估计年度净群落生产（ANCP）通过氧质量平衡，和新的生产（NP）通过硝酸盐质量平衡，在一个跨年度周期和两个连续的贫营养期。微结构测量将提供急需的垂直扩散率的配置文件，以准确地限制流量的氧气和硝酸盐及其在年度周期的变化。氧/氩比测量将被用作生物介导的氧变化的独立估计值，并作为滑翔机测量的氧浓度变化率的约束条件。通过流式细胞术对浮游植物特征的评估将用于校准滑翔机的光学传感器以适应原位生物特征，从而可以在滑翔机的高时间分辨率下识别浮游植物群落结构和生物量的变化，并与同时测量的真光层上方和下方的NCP、NP和物理水柱结构相关。POC输出将从更深层的后向散射库存推断。观测结果的总和将能够评估三个独立测量的生物碳泵强度代理之间的关系，以及系统如何在年度周期内对环境强迫做出反应，特别关注分层贫营养月份。该奖项反映了NSF的法定使命，并被认为值得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来支持。

Observations and measurements over several decades at locations like the Bermuda Atlantic Time-series Study (BATS) site have been important to fundamental understanding of the links between the physics, chemistry, and biology of the ocean. At the BATS site however, despite the long history of observations, a mystery remains: When and how is enough nitrogen delivered to surface waters to support the biological production that is observed? The investigators will use oxygen, nitrate, and micro-turbulence sensors on autonomous underwater gliders to sample continuously for twenty months at the BATS site in an effort to resolve this mystery. Gliders make it possible to measure processes at scales that can't be captured by monthly or biweekly sampling from a ship. Regular sampling by the BATS program will still be essential to the project, however, by providing opportunities for calibration and validation of the glider sensors as well as ship support for glider deployments and recoveries. The project will also leverage existing private funding from the BIOS-SCOPE project, a multi-institutional microbial marine biogeochemistry initiative at BATS, that will provide partial support for glider operations. The investigators will recruit and advise at least two NSF Research Experience for Undergraduates (REU) students each year, and will incorporate project themes and data into educational programs at their respective institutions. This project will apply new technologies to address several factors believed to perpetuate significant underestimates of nitrate delivery and particulate organic carbon (POC) exports in the Sargasso Sea. High-resolution glider-based observations will be used to estimate annual net community production (ANCP) through oxygen mass balance, and new production (NP) through nitrate mass balance, over a period spanning an annual cycle and two consecutive oligotrophic periods. Microstructure measurements will provide much-needed profiles of vertical diffusivity to accurately constrain fluxes of oxygen and nitrate and their variability over the annual cycle. Oxygen/argon ratio measurements will be used as independent estimates of biologically mediated oxygen changes and as constraints on glider-measured rates of oxygen concentration change. Assessments of phytoplankton characteristics by flow cytometry will be used to calibrate the gliders' optical sensors to in situ biological characteristics, so that variability in phytoplankton community structure and biomass can be discerned at the gliders' high temporal resolution and related to simultaneously measured NCP, NP, and physical water column structure, both above and below the euphotic zone. POC exports will be inferred from backscatter inventories in the deeper layers. The sum of observations will enable assessments of relationships among three independently measured proxies for the strength of the biological carbon pump and how the system responds to environmental forcing over the annual cycle, with particular focus on the stratified oligotrophic months.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.