Collaborative Research: A hydrological seesaw and its effect on alkalinity dynamics in estuaries along a climate gradient

该项目的主要目标是了解浅水河口淡水条件的变化如何影响沉积物产生或消耗的碱度或中和酸的能力。据推测，淡水径流的减少将通过不需要氧气的呼吸过程减少沉积物中的碱度产生；在极端干旱期间，从上述过程中产生的还原化合物，例如还原硫，可以被氧化并产生酸。该项目将考察墨西哥湾西北部三个不同淡水输入量的河口。其中一个河口经历了巨大的淡水径流变化将进行更详细的研究。目的是揭示这些变化与沉积物中还原硫的积累和分解之间的联系。此外，还将评估这些过程对水柱碱度的影响。本研究将测量水柱碱度变化和底栖生物通量，研究沉积记录的历史变化，并进行建模以将实地测量结果联系起来。来自德州农工大学科珀斯克里斯蒂分校（TAMU-CC）和加尔维斯顿德州农工大学（TAMUG）的研究人员将参与这个项目。该团队包括两名早期职业科学家。两个研究生，每个校区一个，将使用这个项目来发展他们的研究。这个项目的成果将用于课堂指导和外展活动。这些活动包括为TAMU-CC正在进行的国家科学基金会国家研究培训计划扩展课程，以及为TAMUG的海上营地开发教学模块，后者为小学生提供服务。众所周知，当近岸沉积物中缺乏有机碳时，微生物可以利用溶解氧以外的电子受体来呼吸有机碳。结果，产生了还原硫，并与有机碳保存一起保存。然而，这种保存的速度并不是恒定的，它取决于河流输送的营养物质和陆地有机碳的数量。这项研究的结果将阐明水文条件在近岸碱度生产和消费中的作用。研究结果也将适用于面临淡水径流减少的其他沿海地区。此外，本项目开发的模型可广泛用于沿海研究和管理的各种应用。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The main goal of this project is to learn how changes in freshwater conditions in shallow estuaries affect how much alkalinity, or acid-neutralizing capacity, the sediments produce or consume. It is hypothesized that a reduction in freshwater runoff will reduce alkalinity production in sediments via respirational processes that do not require oxygen; and during extreme drought, reduced compounds, for example reduced sulfur, produced from the above processes can be oxidized and generates acids. This project will examine three estuaries along the northwestern Gulf of Mexico with different amounts of freshwater inputs. One of the estuaries that experiences large freshwater runoff changes will be studied in more detail. The objective is to unravel the connection between these changes and the buildup and breakdown of reduced sulfur in the sediments. Additionally, the impact of these processes on the alkalinity of the water column will be assessed. This study will measure water column alkalinity changes and benthic fluxes, examine sedimentary record for historical changes, and conduct modeling to tie field measurements together. Researchers from both Texas A&M University-Corpus Christi (TAMU-CC) and Texas A&M University at Galveston (TAMUG) will work on this project. The team includes two early career scientists. Two graduate students, one from each campus, will use this project to develop their research. Results from this project will be used in classroom instructions as well as outreach activities. These activities include expanding the curriculum for an ongoing NSF National Research Traineeship program at TAMU-CC as well as developing a teaching module for Sea Camp at TAMUG, the latter serves elementary school students. It is known that electron acceptors other than dissolved oxygen can be used by microbes to respire organic carbon in nearshore sediments when the latter is absent. As a results, reduced sulfur is produced and preserved along with organic carbon preservation. However, the rate of this preservation is not constant and is subject to the amounts of nutrients and terrestrial organic carbon that rivers deliver. The results of this study will shed light on the role of hydrological conditions in nearshore alkalinity production and consumption. The findings will also be applied to other coastal regions in the face of decline in freshwater runoff. In addition, the model developed in this project can be used in a wide variety of applications in coastal research and management.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.