Oak Ridge Institute for Science and Education Fellow, United States Environmental Protection Agency, Office of Research and Development, Center for Environmental Measurement & Modeling, Atlantic Coastal Environmental Sciences Division, 27 Tarzwell Drive, Narragansett, RI, 02882, USA.
United States Environmental Protection Agency, Office of Research and Development, Center for Environmental Measurement & Modeling, Atlantic Coastal Environmental Sciences Division, 27 Tarzwell Drive, Narragansett, RI, 02882, USA.
J Environ Manage. 2024 Mar;355:120478. doi: 10.1016/j.jenvman.2024.120478. Epub 2024 Mar 2.
Anthropogenic nutrient loading has resulted in eutrophication and habitat degradation within estuaries. Study of eutrophication in estuaries has often focused on larger systems, while there has been increasing interest in understanding the governing processes in smaller systems. In this study, we incorporate both monitoring data and mechanistic modeling to improve our understanding of eutrophication in a small, shallow New England estuary. High-frequency continuous and discrete water quality samples were collected from 2018 to 2020 along a salinity gradient and at varying depth to provide temporal and spatial resolution of the system. Conditions of this estuary were simulated using the Hydrological Simulation Program - FORTRAN (HSPF) and the Water Quality Analysis Simulation Program (WASP) to develop a mechanistic, numerical fate and transport model. Our findings suggest complex hydrodynamics with three distinct salinity gradients and variability in salinity concentration upstream. Simulated and observed nutrient trends demonstrated decreasing total nitrogen concentration moving downstream and low total phosphorus concentration throughout the system. Simulated nutrient depletion and shading via macroalgae suggest their importance in similar modeling initiatives. Dynamic spatiotemporal variability in dissolved oxygen concentrations ([DO]) resulted from hydrodynamic and ecological processes such as large, rapid swings in phytoplankton. Carbonaceous biological oxygen demand was suggested to be the driver of hypoxia in surface waters, while sediment oxygen demand may drive low [DO] in the stratified, benthic waters. These findings suggest that the coordination of monitoring and modeling was important to understanding the governing mechanisms of eutrophication and hypoxia. Insights from this study could be used to support regional management strategies to increase [DO], improve water clarity, and recover indigenous seagrass beds. This work has the potential to inform future study and management of small, complex estuaries.
人为营养负荷导致了河口富营养化和生境退化。对河口富营养化的研究通常集中在较大的系统上，而对较小系统的控制过程的兴趣日益增加。在这项研究中，我们结合监测数据和机理模型来提高对一个小型、浅新英格兰河口富营养化的理解。从 2018 年到 2020 年，我们沿着盐度梯度和不同深度采集了高频连续和离散的水质样本，以提供系统的时间和空间分辨率。该河口的条件使用水文模拟程序 - FORTRAN (HSPF) 和水质分析模拟程序 (WASP) 进行模拟，以开发一个机理、数值的归宿和输运模型。我们的研究结果表明，该河口存在复杂的水动力，有三个不同的盐度梯度，上游盐度浓度变化较大。模拟和观测到的营养物趋势表明，总氮浓度在下游逐渐降低，整个系统的总磷浓度都很低。模拟的营养物消耗和大型藻类的遮光表明它们在类似的建模工作中很重要。溶解氧浓度 ([DO]) 的动态时空变异性是由水动力和生态过程引起的，如浮游植物的大幅快速波动。建议碳源生物需氧量是表层水缺氧的驱动因素，而底栖水层的沉积物需氧量可能会导致低 [DO]。这些发现表明，监测和建模的协调对于理解富营养化和缺氧的控制机制很重要。本研究的结果可用于支持区域管理策略，以增加 [DO]、提高水清晰度和恢复本地海草床。这项工作有可能为未来对小型、复杂河口的研究和管理提供信息。
