Influence of oceanic water masses on aragonite saturation and pH in a fringing reef
In order to describe the seasonal variability of the carbonate system in the northern-most coral reef of the eastern Pacific, we collected water samples every month along a year and deployed a temperature-salinity sensor to record high-frequency variability. We found two conditions on the reef: summer with the presence of Tropical Surface Water (TSW), characterized by high temperature, lower DIC levels, and a higher aragonite saturation ); and winter with Gulf of California Water (GCW), when the opposite occurred. This seasonal variation was due to the horizontal advection of two surface water masses: GCW during winter and TSW the rest of the year as a result of the ocean circulation at the entrance of the gulf of California. Therefore, the reef is significantly influenced by open ocean waters, where the depth is less than 20 m. The seasonal variation in ) between months with the presence of GCW and TSW is one of the largest ranges reported in coral reefs = 0.5 units). Our results suggest that the reef community cannot modify the aragonite or pH of incoming water. This might be the case of other fringing reefs, where the use of ocean acidification forecast models is suitable.