Award: OCE-1760747

The impacts of hurricanes Harvey and Nate in August and October 2017 on coastal carbon and oxygen (O2) concentrations and controlling processes on the Louisiana-Texas Shelf were investigated based on three research cruises conducted in July, September, and October. Prior to the cruises, we had hypothesized that the seasonal development of linked hypoxia and acidification would break down and reform differently following tropical storms because O2 is poorly buffered to physical mixing and exchange with the atmosphere whereas dissolved inorganic carbon (DIC) and the carbonate system are strongly buffered. Further, O2 and DIC would be impacted differently by the large amount of sediment resuspension that occurs during hurricanes. To test this hypothesis, we observed changes in water-column concentrations of O2/Ar, pCO2, pH organic matter, and nutrients and changes in process rates for water-column primary production and respiration and sediment fluxes of dissolved O2, DIC, and alkalinity following hurricanes. Following Hurricane Harvey, average surface pCO2 was higher (453 matm) than normal and net respiration (mean = -5 mmol O2 m-3 d-1) prevailed in the water-column across the shelf. During the October cruise, Hurricane Nate crossed through our sampling area mid-cruise. Following Nate, the water-column was well-mixed and there was increased sediment resuspension and water-column and sediment respiration resulting in O2 uptake and DIC release. These processes led to higher pCO2 and lower pH in the surface and bottom water than the pre-storm conditions. The results supported our hypothesis that the storms more strongly impacted O2 concentrations by resetting equilibrium with the atmosphere through mixing. Last Modified: 12/15/2020 Submitted by: John C Lehrter