Benthic Biogeochemical Exchange Dynamics on the Oregon Shelf

关于在海洋东部边界的沿海大陆架区域形成低氧带的长期理论指出，来自大陆架外的缺氧水上涌。换句话说，来自大陆架断裂以外的溶解氧耗尽的致密水沿着海底向上被吸引到大陆架上，与那里的含氧水混合，形成低氧区。这个项目的研究人员试图通过分析陆架沉积物中呼吸作用的附加效应来改变这一范式。研究人员假设，由于上覆水域输入的有机物的季节性变化，沉积物的生物活性发生了变化，这是深层陆架水溶解氧含量变化的主要因素，可能是缺氧区形成的主要变量。虽然现场分析将局限于俄勒冈州的边缘，但在缺氧带形成的其他沿海地区，本研究具有很大的适用性。除了有可能解开物理和生物地球化学过程之间复杂的局部反馈之外，研究人员还计划与一家名为分析仪器系统的小公司合作，建立一种新的氧气传感器，称为旋转圆盘微电极（RDME），它不会干扰其测试的环境，并且可以比目前流行的传感器——微光电二极管——部署更长的时间。她的RDME将与微型光电装置一起部署，以进行比较，并验证RDME在沿海生态系统研究中的必要性。该项目将为一名博士后、一名研究生和三名本科生提供独特的体验。将建立一个公共数据库，这将极大地帮助任何对类似研究感兴趣的人获得和存档数据。该数据库将与各种其他海洋观测数据产品相连接，这将使研究界和公众能够在这一特定研究领域之外建立联系。这位研究者在她的研究中有很强的记录，包括本科生（REU）学生的研究经历，她将继续在这个项目中这样做。研究人员旨在挑战俄勒冈大陆架上的缺氧区是由大陆架上的缺氧水上涌造成的，而当地的大部分初级生产力在下涌期间被出口到大陆架上。初步数据表明，季节性底栖生物呼吸可能是大陆架上缺氧水形成的一个主要因素。利用涡旋相关测量、沉积物岩心培养和近海床颗粒有机物（POM）收集，将表征俄勒冈边缘每个季节的生物地球化学通量。这项工作本身是雄心勃勃的，但研究人员还计划开发一种名为旋转圆盘微电极（RDME）的新型氧传感器，在进行涡流相关测量时，将其与目前流行的微光电器件进行比较。RDME将足够小，不会干扰原位测量的物理性质；它对流不敏感，可部署更长时间。该项目不仅有可能彻底推翻目前关于陆架边缘缺氧带形成的最佳理论，而且涡旋相关方差的使用对动态沿海生态系统的研究是新的，并将对陆架底栖生物的生物地球化学过程产生深刻的见解。

The longstanding theory regarding the formation of low oxygen zones in coastal shelf regions at the eastern boundaries of the oceans has pointed to the upwelling of oxygen-depleted waters from off of the shelf. In other words, dense water from beyond the shelf break that is depleted in dissolved oxygen is drawn along the seafloor upwards onto the shelf, mixing with the oxygenated water there, and creating low oxygen (hypoxic) zones. This is a paradigm that the researcher in this project seeks to shift by analyzing the added effects of respiration in shelf sediments. The investigator hypothesizes that changes in the biological activity of sediments due to seasonal changes in organic matter input from overlying waters are a major factor in the changes in dissolved oxygen content of deep shelf water, perhaps being the leading variable in the creation of hypoxic zones. Though the field analysis will be confined to the Oregon margin, there is a great deal of applicability for this research in other coastal regions where hypoxic zones form. In addition to the potential for unraveling complex local feedbacks between physical and biogeochemical processes, the researcher plans to work with a small business called Analytical Instrument Systems to build a new oxygen sensor, called a rotating disc microelectrode (RDME), that does not intrude on the environment it is testing and that can be deployed for much longer periods of time than currently popular sensors, micro-optodes. Her RDME will be deployed with micro-optodes for comparison and to validate the necessity for the RDME in the study of coastal ecosystems. This project will provide a unique experience for a postdoctoral researcher as well as a graduate and three undergraduate students. A public database will be created which will greatly help with accessibility and archiving of data for anyone who is interested in similar research. The database will be connected with a variety of other ocean observing data products, which will allow the research community and the public to make connections outside of this particular field of study. This investigator has a strong track record of including Research Experiences for Undergraduates (REU) students in her research, and she will continue to do so in this project. The researcher aims to challenge the paradigm that hypoxic zones on the Oregon shelf are created by upwelling of offshelf oxygen-depleted water and that most of the local primary productivity is exported off the shelf during downwelling periods. Preliminary data suggests the possibility that seasonal benthic respiration may be a major factor in hypoxic water formation on the shelf. With the use of eddy covariance measurements, sediment core incubations, and near seabed particulate organic matter (POM) collections, the biogeochemical fluxes of the Oregon margin will be characterized for every season. This work is ambitious on its own, but the investigator also plans to incorporate the development of a new oxygen sensor called a rotating disc microelectrode (RDME) that will be compared to currently popular micro-optodes when making eddy covariance measurements. The RDME will be small enough as not to interfere with the physical properties being measured in situ; it will be insensitive to flow and deployable for longer periods of time. Not only does this project contain the possibility of completely overturning the current best theory of hypoxic zone formation on shelf margins, but the use of eddy covariance is new to the study of dynamic coastal ecosystems and will yield great insights into the biogeochemical processes of shelf benthos.