The results showed that coral calcification rates decrease significantly along a natural gradient in seawater pH. Ocean acidification lowers the concentration of carbonate ions in seawater, making it more difficult for corals to build their calcium carbonate skeletons.
"Carbonate ions are the building blocks they need to grow their skeletons. When the pH is lower the corals have to use more energy to accumulate these carbonate building blocks internally. As a result, the calcification rate is lower and they lay down less dense skeletons," Paytan said.
The reduced density of the coral skeletons makes them more vulnerable to mechanical erosion during storms, organisms that bore into corals, and parrotfish, which sometimes feed on corals. This could lead to a weakening of the reef framework and subsequent degradation of the complex coral reef ecosystem.
"There are likely to be major shifts in reef species and some loss of coral cover, but if ocean acidification is the only impact there won't be total destruction," Paytan said. "We need to protect corals from other stressors, such as pollution and overfishing. If we can control those, the impact of ocean acidification might not be as bad."
|Contact: Tim Stephens|
University of California - Santa Cruz