Risk of Coral Reef Damage: Increased Due to High Ocean Acidity

In a concerning development for the world's coral reefs, a new study suggests that ocean acidification will cause more dissolution of calcium carbonate, a key reef building block, than its production in the near future.

The study, led by Australia's Southern Cross University and involving scientists from the University of California San Diego, was published in the journal Science on Feb. 23. Co-authors include Scripps chemical oceanographers Tyler Cyronak and Andreas Andersson.

Ocean acidification is a result of the use of fossil fuels and other human activities that have raised levels of the greenhouse gas carbon dioxide to the highest in human history. As seawater CO2 increases, the pH falls, making it more difficult for shell-forming organisms to create calcium carbonate.

Professor Bradley Eyre from Southern Cross University's Centre for Coastal Biogeochemistry, the study lead author, explains the situation as a savings account, suggesting that withdrawals (dissolution) will exceed deposits (coral calcification) in the next few decades.

Organic matter lowers seawater pH faster, especially in sediments where it is broken down by microbial respiration. This means that coral reefs, which are particularly vulnerable due to ocean warming, coral bleaching, and their proximity to land masses, are at an increased risk.

The consequences of this imbalance will depend on both the size of the savings (amount of calcium carbonate) and the difference between deposits and withdrawals. The sediment that serves as the foundation of most coral reef ecosystems could begin to erode within 30 years due to increasing ocean acidity.

Dissolution rates of the sands were more sensitive to ocean acidification than coral calcification, as noted by Cyronak. The response of sediment dissolution to increasing CO2 was consistent across various sand types and coral reef ecosystems.

The researchers' findings do not imply that entire reefs will dissolve, as corals will continue to calcify. However, this dissolution of calcium carbonate will exacerbate reef loss, and in some regions such as Hawaii, it has already begun.

Andersson suggests that the situation is akin to a savings account where withdrawals exceed deposits. The consequences will depend on both the size of the savings and the difference between deposits and withdrawals.

The study's findings emphasize the need for urgent action to combat ocean acidification and protect coral reef ecosystems. Some coral reef ecosystems face a decline in sands used for building and maintenance, according to the study.

The researchers involved in the study "Coral reefs will transition to net dissolving before end of century" include scientists from the University of Technology Sydney and James Cook University, besides those from Southern Cross University. The study's findings underscore the urgent need for global efforts to reduce greenhouse gas emissions and protect our world's coral reefs.