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

NSF Award Abstract: 

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.