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区的长期理论指出，大陆架外的贫氧沃茨会涌上。换句话说，来自大陆架断裂处以外的溶解氧耗尽的浓水被沿着海底向上吸引到大陆架上，与那里的含氧水混合，形成低氧（缺氧）区。这是一个范例，在这个项目中的研究人员试图通过分析陆架沉积物中呼吸的附加影响来改变。研究人员假设，沉积物的生物活性的变化，由于季节性变化的有机物输入上覆沃茨是一个主要因素的变化，溶解氧含量的深架水，也许是在创建缺氧区的主要变量。虽然现场分析将被限制在俄勒冈州的边缘，有很大的适用性，在其他沿海地区的低氧区形成这项研究。除了解开物理和地球化学过程之间复杂的局部反馈的潜力外，研究人员计划与一家名为分析仪器系统的小企业合作，建立一种新的氧气传感器，称为旋转圆盘微电极（RDME），它不会侵入它正在测试的环境，并且可以部署比目前流行的传感器更长的时间，微光电二极管。她的RDME将与微光管一起部署，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研究人员以及一名研究生和三名本科生提供独特的经验。将建立一个公共数据库，这将大大有助于对类似研究感兴趣的任何人访问和存档数据。该数据库将与其他各种海洋观测数据产品连接，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。这位研究员在她的研究中包括本科生（REU）学生的研究经验方面有着良好的记录，她将继续在这个项目中这样做。研究人员的目的是挑战这样一种范式，即俄勒冈州大陆架上的缺氧区是由大陆架外缺氧水的上涌造成的，而当地的大部分初级生产力是在下涌期间从大陆架上输出的。初步数据表明，季节性底栖呼吸可能是大陆架缺氧水形成的一个主要因素。利用涡度协方差测量，沉积物芯孵化，和近海底颗粒有机物（POM）的收集，俄勒冈州边缘的地球化学通量的特点是每个季节。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，在进行涡动协方差测量时，将其与目前流行的微电极进行比较。RDME将足够小，不会干扰现场测量的物理特性;它对流动不敏感，可部署更长的时间。这个项目不仅包含了完全推翻目前最好的理论，在大陆架边缘的缺氧区形成的可能性，但涡度协方差的使用是新的动态沿海生态系统的研究，并将产生很大的见解，大陆架底栖生物的生物地球化学过程。

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.