| Summary: | The ocean plays a vital role in making up 70% of the Earth’s surface, producing over half of oxygen globally, and absorbing approximately 30% of anthropogenic CO2 since the industrial revolution. Ocean acidification (OA) is a direct threat to many organisms living in the oceans across the globe, yet the state of carbonate chemistry and the rate of OA vary in different parts of the world’s oceans. Although current data suggest that the open Gulf of Mexico (GOM) surface waters have relatively high pH (> 8) and aragonite saturation state (ΩArag > 3), the GOM could still experience ecological impacts of OA. In addition, the combination of increasing atmospheric CO2, upwelling, and increasing terrestrial nutrient export may acidify the coastal waters even further. Acidifying ocean waters have decreasing ΩArag, posing serious threats to calcifying organisms, affecting their populations, growth patterns, and shell or skeletal density. The GOM is home to the northernmost tropical coral reefs around the contiguous United States as well as prominent shellfish industry. Historical water column carbonate measurements are scarce, so the progression of OA in the GOM is poorly understood. Research regarding OA in the GOM is needed to manage and protect these resources. In the literature, multiple linear regression (MLR) models have been created to fill data gaps in different ocean regions such as the Gulf of Alaska, the Southern Ocean, the Sea of Japan, and coasts of the northeastern and northwestern United States. Prior to this study, no statistical model existed for carbonate chemistry parameters (i.e., pH and ΩArag) in the GOM. By creating models built upon the relationships between commonly measured hydrographic properties (salinity, temperature, pressure, and dissolved oxygen (DO)) and pH as well as ΩArag, data gaps can be filled in areas that do not have sufficient sampling coverage. In this study, I created statistical models for the estimation of ΩArag and pH in the northwestern GOM (NWGOM) from latitudes ...
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