Banse Early Career Scientist Seminar, 18 Oct 2023
Wednesday, October 18, 03:30 PM to 04:30 PM PDT
Wednesday, October 18, 03:30 PM to 04:30 PM PT, with tea and cookies to follow
Ocean Sciences Building (OSB), Room 425
Larissa Dias, NOAA PMEL
ABSTRACT
Marine waters are acidifying at an alarming rate, yet high variability in coastal regions and overall sparse data create obstacles to better understanding baseline and changing conditions in the carbonate chemistry of these systems. Since coastal and ocean acidification can have major negative impacts on resident species, with resultant impacts on ecosystems and human activities (e.g., tourism, fisheries), gaining a better understanding of this acidification is imperative. In this talk, the overarching themes of three interrelated studies and creation of data products are discussed. Innovative methods in studying changing marine carbonate chemistry are examined, tracing a geographic route from rivers to estuaries to the open ocean. First, long-term trends in river alkalinity load and concentration were modeled and compared to long-term trends in total alkalinity (TA) of adjacent estuaries in the northwestern Gulf of Mexico (GOM). River alkalinity concentration and yield were declining significantly in some rivers, while estuarine TA was declining significantly in the southernmost estuaries. Second, seasonal patterns in CO2 flux and carbonate chemistry and their relations to freshwater inflow and biological activity were examined in Galveston Bay, an urbanized estuary located in the northwestern GOM. Galveston Bay was a net sink for atmospheric CO2 (-8.26 ± 17.33 mmol m-2 d-1), yet high spatial and temporal variability caused portions of this Bay to behave as a source of CO2 in winter, fall, and summer. Third, a novel approach of sediment core incubation was conducted to determine the contribution of the oxidation of sedimentary reduced sulfur species to overall estuarine TA consumption in Mission-Aransas Estuary, a subtropical and semiarid estuary of the northwestern GOM. This estuary had a previously unidentified TA sink, and results provided evidence that sedimentary oxidation of reduced sulfur species consumes TA in this estuary.
Current works have shifted scientific focus towards addressing the need for more efficient use of open ocean data, which has vastly increased in quantity due to international efforts at deploying autonomous devices such as biogeochemical Argo floats. While these floats have the potential to revolutionize our understanding of open ocean carbonate chemistry and biogeochemistry, methods for accurately obtaining a secondary constraint for carbonate system quantification, calibrating the float pH sensors, and for quality control are needed to optimize use of the data. Data products and methods that are developed with this aim additionally need to be readily available. In prior research, empirical seawater property estimation routines (ESPERs) were developed to help with the sensor calibration and secondary constraint issues. Python language translations of ESPERs (from original MATLAB language) and updates to ESPERs to include additional training and validation data, novel methods for incorporation of anthropogenic carbon, homogenization of pH (along with complete metadata), and an automated algorithm-based Quality Control assistance tool are in progress. This project also aims to further examine whether the recent hypothesis that the pH-dependent pH discrepancy between spectrophotometric pH and pH calculated from TA and dissolved inorganic carbon (DIC) can be partially attributed to alkaline organic molecules. Altogether this work provides meaningful new tools to improve research on coastal and ocean acidification and biogeochemistry
