Hydrological controls on the distribution of dissolved inorganic carbon and total alkalinity in a northwestern Gulf of Mexico estuary

Coastal regions are recognized as areas of significant biogeochemical activities, primarily due to the influx of nutrients from rivers. However, under the influence of climatic changes, these riverine fluxes are diminishing, significantly altering the biogeochemistry of coastal regions. Such changes could also impact carbon chemistry in these regions, affecting the health of ecosystems. Therefore, it is imperative to conduct long-term studies to monitor the impact of these hydrological changes on the carbon chemistry of coastal systems. In this study, we conducted an analysis of a decadal time series data on dissolved inorganic carbon (DIC) and total alkalinity (TA), along with physicochemical parameters (including pH, Temperature, Salinity), in the Mission-Aransas estuary, located in the northwestern Gulf of Mexico. These samples were collected at five stations from April 2014 to August 2025. Our focus was on characterizing the sources and sinks of DIC and TA and evaluating the hydrological impacts on carbonate parameters. The results show both non-conservative removal and gain of DIC and TA from the mixing line between river water and seawater. Gain of DIC and TA is mainly observed