Southeast Asian Coral Reefs - Ocean Acidification

Ocean Acidification

One of the largest potential threats of ocean acidification to marine invertebrates is the corrosive properties of undersaturated waters with respect to calcium carbonate skeletons/shells, and a theoretical inability to calcify under these conditions. Ocean acidification is a lowered pH of ocean waters caused by increased carbon dioxide emissions into the atmosphere, which results in more CO2 dissolving into the ocean. This poses a threat to corals and calcifying macroalgae, two main calcifying groups that occur in reefs, as well as other shelled organisms and the organisms that depend on them. Corals and calcifying macroalgae such as coralline red algae and calcifying green algae are extremely sensitive to ocean acidification because they build their hard structures out of calcium carbonate. The sinking pH of ocean waters makes it difficult for these shelled creatures to produce enough calcium carbonate to build and maintain their skeletal structures. Echinoderms, such as sea stars and sea urchins, and mollusks, including squid and clams, as well as many other species are also at risk because of thinning shells and weakened skeletal structures. By targeting calcifying organisms, ocean acidification threatens the health of reef ecosystems as a whole.

Ocean acidification from increasing level of atmospheric CO2 represents major global threats to coral reefs, is in many regions exacerbated by local-scale disturbances such as overfishing. Studies have shown that severe acidification and warming alone can lower reef resilience even under high grazing intensity and low nutrients. Furthermore, the threshold at which herbivore overfishing (reduced grazing) leads to a coral-algal phase shift was lowered by acidification and warming. Also, increasing temperature and ocean acidification are predicted to have a synergistic effect; ocean warming will further magnify ocean acidification changes.