Benthic Biogeochemical Exchange Dynamics on the Oregon Shelf

关于在大洋东部边界的沿海陆架区域形成低氧区的长期理论指出，从陆架外涌出了氧气枯竭的水域。换句话说，来自陆架断裂以外的、溶解氧耗尽的致密水沿着海底向上拉到陆架上，与那里的含氧水混合，形成低氧(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影响来改变这一范式。研究人员假设，由于上覆水域输入的有机质的季节性变化，沉积物的生物活性发生了变化，这是深水架水溶解氧含量变化的主要因素，可能是形成低氧带的主要变量。虽然现场分析将局限于俄勒冈州边缘，但这项研究在其他形成低氧带的沿海地区也有很大的适用性。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企业合作，建立一种新的氧传感器，称为旋转圆盘微电极(RDME)，它不会干扰它正在测试的环境，而且可以比目前流行的传感器微光电极部署更长的时间。她的RDME将与微光电进行比较，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研究员以及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取和存档数据。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。这位调查员在她的研究中包含了本科生的研究经验，并且她将继续这样做。这位研究人员的目标是挑战这样一种范式，即俄勒冈州大陆架上的缺氧区是由陆外耗氧水的上涌造成的，而当地的大部分初级生产力在下升流期间是从陆架输出的。初步数据表明，季节性底栖生物呼吸可能是大陆架上形成低氧水的主要因素。通过使用涡旋协方差测量、沉积物岩心培养和近海底颗粒有机质(POM)收集，俄勒冈州边缘的生物地球化学通量将在每个季节得到表征。这项工作本身雄心勃勃，但研究人员还计划开发一种名为旋转圆盘微电极(RDME)的新氧传感器，在进行涡流协方差测量时，将与目前流行的微光极进行比较。RDME将足够小，不会干扰现场测量的物理性质；它将对流动不敏感，并可在更长的时间内展开。该项目不仅有可能完全颠覆目前最好的陆架边缘低氧带形成理论，而且涡旋协方差的使用对动态沿海生态系统的研究是新的，并将对陆架底栖动物的生物地球化学过程产生巨大的洞察。

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.