As the acid level in ocean water increases, the carbonate sand on coral reefs decreases . According to one study, this decline will begin in an average of about three decades .
For thousands of years, the decomposing remains of coral, as well as other reef organisms, have allowed the formation of carbonate sands . These have become the ‘building material’ for coral reef frames and shallow reef environments such as lagoons, reef flats, and coral sand cays.
This type of terrain is sensitive to the chemical composition of the sea . Much of the carbon dioxide that humans emit is absorbed by the world’s oceans (it is estimated that to date they have already absorbed a third of the CO2 produced). The impact of this absorption means that the oceans become impregnated with carbon dioxide, they become acidic and, at a certain point, the carbonate sands begin to dissolve.
Acidification also produces a reduction in the amount of carbon produced by corals. The study has shown that reefs face a double consequence of this poisoning. On the one hand, the amount of carbonate material produced will decrease, and on the other hand, newly produced and stored carbonate sands will also dissolve.
Few solutions
For the research, a series of underwater cameras were placed over different coral reef sands. Specifically in 22 locations on Heron Island (Australia), Hawaii, the Bermuda and Tetiaroa islands, reefs of the Pacific and Atlantic oceans.
The results show that the speed at which the sand dissolves is related to the acid levels in the water that covers it . This indicates that corals have the ability to adapt to new acidic conditions, but the same does not happen with sandy soil as it is a geochemical process.
The reef samples revealed that the response to future ocean acidification is the same. However, the different starting conditions of each location have a different impact on each other. For example, the carbonate sands in the Hawaii area are already in the process of dissolving, while those in Tetiaroa have not yet started.
Despite this variation, it is estimated that by the end of the century they will experience a complete dissolution of the sands . What is unknown, at the moment, is whether an entire reef will slowly erode or collapse once the sediments are completely dissolved. One way or another, the truth is that there is no effective solution to this problem. At the moment, the impact of ocean acidification can only be reduced by managing the impact of organic matter such as algae on a local and regional scale.
Citation: Bradley D. Eyre, Tyler Cyronak, Patrick Drupp, Eric Heinen De Carlo, Julian P. Sachs, Andreas J. Andersson. “Coral reefs will transition to net dissolving before end of century”. Science (2018) DOI: 10.1126 / science.aao1118
