Ocean Acidification trends in the Gulf of Mexico: the GOMECC program

Ocean acidification (OA) is a consequence of the absorption of anthropogenic CO2 by the oceans and poses an increasing threat to marine ecosystems and coastal economies that rely on marine resources. Since 2007, the NOAA Ocean Acidification Program (OAP) supports synoptic cruises along the coasts of the conterminous United States as part of its commitment to monitor coastal ocean acidification conditions. The Gulf of Mexico (GoM) is a low-latitude, semi-enclosed basin. The GoM is strongly influenced by the Loop Current and, in the northern section, by riverine inputs from the Mississippi River. The eastern section of the GoM has been experiencing devastating Harmful Algal Blooms some of which lasted 16 months (2017-2019). A sustained heat wave in 2023 caused mass mortality in the coral reefs of the Florida Straits. OA can act as a co-stressor further contributing to the impacts of these phenomena. Four Gulf of Mexico Ecosystems and Carbon Cycle (GOMECC) cruises have been conducted during the summer in 2007, 2012, 2017 and 2021 with support from NOAA OAP. Multiple near-shore (~15m depth) to open ocean (~3000m depth) transects are conducted during these cruises. Parameters measured include pH, total alkalinity (TA), dissolved inorganic carbon (DIC) and fugacity of CO2 (fCO2), as well as O2, nutrients, salinity, and temperature. Underway instruments measure surface water and atmospheric fCO2 to determine air-sea CO2 fluxes. Since 2017, biological studies have been incorporated to the cruises, to characterize plankton communities, evaluate rate measurements of growth and grazing to track carbon flow to higher trophic levels, and estimate active carbon export flux due to diel vertically migrating zooplankton. Here we present an overview of the program and results from our most recent cruise, and we look at trends in carbon parameters over the history of the GOMECC program, exploring regional differences within the GoM.