Ocean acidification (OA) is the process by which sea water absorbs atmospheric carbon dioxide (CO2). As the concentration of CO2 in seawater increases, it causes the pH and the carbonate (CO3-) ion concentration within the seawater to decrease. This lowered pH can make it impossible for certain species to survive, which in turn can have catastrophic effects ecosystems. OA is monitored through the measurement of dissolved inorganic carbon, pCO2, pH, and total alkalinity (TA). The OA monitoring program in Tampa Bay has found that the measured TA is higher than the calculated TA. In this study, we sought to determine if organic alkalinity from dissolved organic carbon (DOC) could be responsible for the difference between measured and calculated TA, and if so, what the predominate forms of organic matter present were. DOC was characterized via Fourier-Transform Ion Cyclotron Resonance Mass Spectrometry. Phosphate, silicic acid and pH were evaluated using absorbance-based methods, and total CO2 was determined via titration in an open vessel. Measured TA was on average 20 µmol/kg greater than the calculated TA. Nutrient analysis indicated that although silicic acid and phosphate are present in Tampa Bay, these nutrients contributed approximately 2 µmol/kg to TA. However, the contribution of DOC suggested that organic compounds could be responsible for 8 µmol/kg of the TA of alkalinity. This indicated that the organic alkalinity is likely responsible for 40% of the difference between measured and calculated TA. The average mass to charge ratio of the organic milieu was 350, with most compounds ranging from 200-500, and van Krevlen analysis indicates that most organic compounds were proteins.

Tampa Bay ocean acidification and the influence of dissolved organic carbon on accurate carbonate system measurements

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.