Ocean Acidification will Severely Impair Coral Reef Growth by the End of the Century
New research on Australia’s Great Barrier Reef led by Carnegie Institution for Science’s Ken Caldeira and the California Academy of Sciences’ Rebecca Albright show that ocean acidification will severely impair coral reef growth by the end of the century if carbon dioxide emissions continue to rise. The scientists performed the first ocean acidification experiment. They made seawater artificially acidic by adding carbon dioxide and then allowing it to flow across a natural coral reef community. The acidity of the seawater increased, thus reflecting end-of-century projections if we do not lower carbon dioxide from greenhouse gas emissions.
According to some statistics, half of the world’s coral has been lost since the 1980s. Corals are delicate animals and we manage to endanger them or threaten their existence as we contribute to sea pollution. Coastal constructions’, sediments, waste, sewage, farmland run-off and fishing are also factors that contribute to coral demise.
The biggest threats to coral are warming seawater and the carbon dioxide absorbed into the ocean, where it remains for millennia. Ocean heatwaves in 2015, 2016 and 2017 finished off an astonishing 20% of the coral on Earth. This is troubling, for countless wildlife depends on coral reefs for their survival. Losing even more coral would cause huge disruption to the ocean’s ecosystems, which would, in turn, disturb coastal ecosystems.
The chemical reaction between the seawater and deep-water carbon emissions produces carbonic acid, which is corrosive to coral reefs, shellfish, and other marine life. Coral reefs are especially vulnerable to the ocean acidification because their skeletons go through the process of calcification in order to evolve. If you want an example closer to home, think about your teeth: the more acidic your mouth environment is, the more vulnerable to erosion and cavities your calcium-teeth become.
Caldeira and Albright’s study shows “strong evidence that ocean acidification caused by carbon dioxide emissions will severely slow coral reef growth in the future unless we make steep and rapid reductions in greenhouse gas emissions.”
By working in controlled areas of a natural coral reef community and experimentally manipulating seawater chemistry, Caldeira, Albright, and their team managed to show how ocean acidification affects coral reefs on the ecosystem scale, not just in terms of individual organisms or species, as other previous studies have done.
The scientists are not at their first experiment of this sort. Two years ago, Caldeira and Albright published a breakthrough study providing evidence that ocean acidification is already slowing coral reef growth. In the previous study, they made the corals’ environment more alkaline – in other words, they fed the reef an antacid. The experiment demonstrated that the coral reef fared better under these circumstances. An alkaline environment led to the coral’s ability to better construct its architecture.
After they altered seawater chemistry of reef flats surrounding One Tree Island off the coast of Australia, the scientists explained that: “Last time, we made the seawater less acidic, like it was 100 years ago, and this time, we added carbon dioxide to the water to make it more acidic, like it could be 100 years from now.”
The results are grim, to say the least. While the study findings are crucial to understanding the full scope and complexity of ocean acidification’s impact, as well as to predicting how acidification will affect the coastal communities that depend on these ecosystems.
According to the study’s authors, “there is not a moment to lose in building an energy system that doesn’t dump its waste into the sky or sea.”
As we previously reported, coral reefs are in danger due to pollution and human activity. Let us all hope we could do something to reverse and put a stop to the demise of coral reefs.
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