Flower Garden Banks National Marine Sanctuary (FGBNMS) is located on the subtropical shelf edge of the northwestern Gulf of Mexico, approximately 100 nautical miles (190 km) from the Texas-Louisiana border. Hourly pH and pCO₂ data from December 2021 to May 2023 were collected using two autonomous carbonate chemistry sensors (pH and CO₂ partial pressure or pCO₂) deployed on an FGBNMS reef crest at 27 m depth, and the diurnal and seasonal variations in carbonate chemistry were examined. These variations could be explained by temperature (thermal) effects, metabolic activities, water column stratification, and water mass movement. Despite the remoteness and depth of the FGBNMS coral reef ecosystem, the dynamic patterns of carbonate chemistry were similar to those observed in many nearshore, shallow coral reef ecosystems. Dissolved oxygen (DO) dynamics were estimated based on diurnal changes in total dissolved inorganic carbon concentrations, and the results indicated that diurnal variations in DO followed a similar trend with depth, as observed in shallow reefs worldwide. This study highlights the importance of high temporal resolution and long-term monitoring of carbonate chemistry dynamics in coral reef ecosystems, as such data are crucial for better understanding these ecosystems and projecting their potential responses to environmental stressors.
 

Seawater carbonate chemistry,coral reef ecosystem,autonomous sensor,terrestrial discharge,thermal and nonthermal effect