According to a new study, most reefs around the world will be dissolving more quickly than they can regenerate by the end of the century. Within about 30 years, carbonate sands on coral reefs will begin dissolving as the ocean further acidifies.
The study, published on Feb. 22 in the Science journal, claims that the dissolution of carbonate sands is a potentially hazardous effect of ocean acidification, and it's often overlooked. The ocean acidifies when carbon dioxide dissolves out of the atmosphere and hits the ocean, where it causes a chemical reaction and brings down the water's pH level.
Carbonate sands accumulate over thousands of years when reef organisms break down, and they're crucial to the regeneration of coral reefs because they serve as the building material for coral reef frameworks and shallow reef environments such as reef flats, coral sand clays, and lagoons.
The problem is, carbonate sands are highly sensitive to toxic chemicals in seawater. When the ocean becomes too acidic, carbonate sands begin to dissolve, endangering the coral reef population.
Obviously, to maintain the growth of coral reefs, the rate at which carbonate sands dissolve must be far less than the rate of carbonate production. It's no secret that the acidification of the ocean diminishes the amount of carbonate sands corals produce, which in turn reduces the chance of coral reef production. It's a no-win situation, and it will keep on getting worse.
Writing on Phys.org, lead author Bradley Eyre says that the research team found a strong relationship between the dissolution of carbonate sands and the acidity of seawater. Plus, the sands were far more sensitive to acidification than coral growth — about 10 times.
"This probably reflects the corals' ability to modify their environment and partially adjust to ocean acidification, whereas the dissolution of sands is a geochemical process that cannot adapt."
The Coral Reef Tipping Point
The researchers placed underwater chambers over coral reefs in different locations. These chambers contained acidified water to simulate future conditions of the ocean. In all locations, carbonate sands responded similarly to the acidity, but the researchers noted that there might be variations in terms of impact because of different starting conditions.
They discovered that there seems to be some sort of tipping point in local calcium carbonate levels, which, once reached, coral reefs begin to dissolve more rapidly than they can build. One of the test locations was Hawaii, which the researchers noted has already hit this tipping point.
Of course, different parts of the ocean will react in various ways. Not that every reef in the world will hit the aforementioned tipping point simultaneously, but many of them are on that path within the century.
So how can ocean acidification be stopped or let alone be reduced? Well, significant efforts must be done to lower the emission of carbon dioxide, says Eyre.