A recent publication in PNAS has used some principles close to my research to utilize natural pH variability to investigate how corals will likely respond to future ocean acidification. Using natural variability is an important way to gauge a more realistic view of how corals will respond to future changes in ocean acidity.
Ocean acidification is a decrease in seawater pH caused by the rising levels of atmospheric carbon dioxide that results in altered seawater chemistry. Ocean acidification has the potential to threaten the structural integrity of marine calcifies and disrupt metabolic processes.
A new study has used underwater springs that naturally lower the pH of seawater (the lower the pH, the more acidic the environment) to show how corals will likely respond to ocean acidification. The study was conducted along Mexico’s Yucatan Peninsula and focused on the prevalent Caribbean coral Porites astreoides. Led by Elizabeth Crook of UCSC, the researchers monitored seawater chemistry around the springs and took skeletal cores of the corals to look at growth parameters.
The results of this study show that coral calcification rates decrease significantly along a natural gradient in seawater pH and suggest that corals may not be able to fully acclimatize to low pH conditions. At lower pH the concentration of carbonate ions in seawater is also lower, making it harder for corals to build their calcium carbonate skeletons. Consequently, at low pH corals have to use more energy to accumulate the carbonate ions they need to build their structure. Decreased coral density at lower pH threatens the structural integrity of the reef framework.
The results of this study emphasize the need to protect corals from other stressors, such as pollution and overfishing in the hope that controlling these stressors, the impact of ocean acidification may be reduced.