The oceanic water south of Cabo San Lucas, Mexico is an oxygen minimum zone (OMZ.) OMZs lead to greater concentrations of carbon dioxide in the water. The OMZ near Cabo is expanding, causing an increase in CO2 concentrations and a steadily declining pH in the region. As oceanic pH continues to decline, the water undergoes ocean acidification, causing calcium carbonate (CaCO3) shelled organisms to have increased difficulty forming their shells. In the data collected from the ETNP in late March, 2012, the pH ranged from 7.49 off the coast of San Diego, CA to 7.39 near the center of the OMZ at a depth of 800 meters. More data collection in this region is required to gain an appropriate overview of the effects of ocean acidification on the ecosystem as a whole.
Brodland M. L., 2012. Ocean acidification in the Eastern Tropical North Pacific. University of Washington, School of Oceanography Senior Thesis, Academic Year 2011-2012. Thesis.