Impacts of Engineered De-stratification on Estuarine Biogeochemistry

由于营养物污染，湖泊、水库和沿海河口都容易受到水质差的影响。在某些情况下，水生“死区”是在溶解氧浓度变得如此之低的地方形成的，以至于对生物的丰富程度、营养物质的可用性和食物网的组织产生了负面影响。工程脱层是一种技术解决方案，包括使用大型曝气器混合水柱，迫使大气中的氧气进入深水，从而改善这些系统中的氧气条件。本研究项目旨在确定工程脱层的预期和意外后果，特别是其对氧化作用和控制温室气体和毒素产生的化学循环的影响。例如，氧浓度的变化可能影响环境中汞和甲烷的可用性。该研究项目的另一个目标是与县政府和对研究和恢复Rock Creek河口感兴趣的公民科学家合作，该河口与马里兰州的切萨皮克湾相连。了解与工程脱层相关的权衡的关键步骤是记录脱层对生物地球化学和相关生态系统反应的影响。大型工程曝气系统很少安装在潮汐水域。这项研究利用了安装在Rock Creek河口的一个系统，该系统已经在那里应用了近30年。氮、磷、汞和甲烷池对曝气的反应正在被全面记录，与工程脱层相关的生态系统服务（如反硝化）和意外后果（如温室气体排放）正在被量化。研究人员正在使用一种新颖的、用户控制的河口尺度去分层系统来测试剂量-反应关系。他们的重点是了解曝气时间和潮汐时间对生物地球化学反应的影响。在优化曝气方案方面，该研究将为循环耗氧对养分和温室气体循环的影响提供见解。实验数据将用于增强建模工具，以将研究结果扩展到其他慢性缺氧的水生系统。这些新的努力将揭示一个新的和全面的画面，工程脱层可以有效地利用，以减轻氧气消耗和加强营养去除服务。

Lakes, reservoirs, and coastal estuaries are all susceptible to poor water quality as a result of nutrient pollution. In some cases, aquatic "dead zones" are created where dissolved oxygen concentrations become so low that it negatively impacts the abundance of organisms, the availability of nutrients, and the organization of food webs. Engineered de-stratification is a technological solution that includes the use of large scale aerators to mix the water column and to force atmospheric oxygen into deep waters, thereby improving oxygen conditions in these systems. This research project seeks to determine both the intended and unintended consequences of engineered de-stratification, especially in terms of its effects on oxygenation and the chemical cycles that control greenhouse gas and toxin production. For example, changes to the oxygen concentrations may affect the availability of mercury and methane in the environment. Another objective of the research project is to collaborate with county government and citizen scientists interested in studying and restoring the Rock Creek estuary, which is connected to the Chesapeake Bay in Maryland. A critical step in understanding the tradeoffs associated with engineered de-stratification is to document the impacts of de-stratification on biogeochemistry and associated ecosystem responses. Large engineered aeration systems have rarely been installed in tidal waters. This research study capitalizes on a system installed in the Rock Creek estuary, where this technology has been applied for nearly thirty years. The responses of nitrogen, phosphorus, mercury, and methane pools to aeration is being comprehensively documented, and both the ecosystem services (e.g., denitrification) and unintended consequences (e.g. greenhouse gas emissions) associated with engineered de-stratification are being quantified. The researchers are using a novel, user-controlled estuarine-scale de-stratification system for testing dose-response relationships. They are focusing on understanding the effects of aeration time and tidal timing on biogeochemical responses. In optimizing aeration protocols the study will provide insights into the effects of cycled oxygen depletion on nutrient and greenhouse gas cycling. Data from the experiments will be used to enhance a modeling tool to extend findings to other aquatic systems with chronic oxygen depletion. These new efforts will reveal a new and comprehensive picture of how engineered de-stratification can be efficiently utilized to alleviate oxygen depletion and enhance nutrient removal services.