Dissertation Defense Seminar - Larissa Dias

COASTAL MARINE SYSTEM SCIENCE PROGRAM
DEPARTMENT OF PHYSICAL AND ENVIRONMENTAL SCIENCES
TEXAS A&M UNIVERSITY-CORPUS CHRISTI

TITLE: Estuarine Carbonate Chemistry in the Northwestern Gulf of Mexico and Its Controlling Factors

GRADUATE ADVISOR: Dr. Xinping Hu

ABSTRACT

Subtropical estuaries in the northwestern Gulf of Mexico (nwGOM) exhibit a general long-term decrease in pH and alkalinity, which is more extreme at lower latitudes. This dissertation aims to identify the drivers of carbonate chemistry in these estuaries, which will help elucidate the role of subtropical estuaries in the global carbon cycle. In Chapter II, both sediment incubation experiments and water column chemical analyses were conducted for the semiarid Mission-Aransas Estuary. Changes in total alkalinity (TA) and ion concentration suggested biogeochemical consumption of TA via oxidation of reduced sulfur species during periods of low river inflow. In Chapter III, multidecadal trends in alkalinity and discharge of six major nwGOM rivers were determined. Multiple linear regression methods were used to generate models for predicting downstream estuarine TA based on freshwater variables. Declining freshwater discharge and alkalinity were identified in several of the study rivers, and estuarine alkalinity could be predicted by freshwater alkalinity flow-weighted concentration in many of the models. In Chapter IV, CO₂ flux of the Trinity-San Jacinto Estuary was studied and this estuary was found to be a net sink for atmospheric CO₂ on an annual scale, but with high spatial and temporal heterogeneity driven by freshwater inflow and photosynthesis. The results of this research highlight the important interactions between hydrology and biogeochemistry in regulating the estuarine carbonate system.

Watch via Zoom:
https://tamucc.zoom.us/j/6932539494

Meeting ID: 693 253 9494