Researchers found that corals in the brains of the Alcatraze Islands produce about 170 tons of calcium carbonate per year, representing the retention of about 20 tons of carbon in their mineral form.
The amount of carbon produced and held by the brain corals is equivalent to the carbon emissions of 324,000 liters of gasoline.
The authors analyzed specimens of brain corals with a skeletal structure composed primarily of calcium carbonate (CACO3).
Using computed tomography images, the researchers calculated the annual growth rate of colonies. We then estimated the production of 170 tons of CACO3 per year.
How calcium carbonate contributes to greenhouse gas emissions
Calcium carbonate is made up of elements such as calcium, oxygen and carbon. The latter binds to oxygen and forms carbon dioxide (CO2), which contributes to the greenhouse effect when released into the atmosphere as a result of the combustion of fossil fuels.
Luis de Souza Oliveira, the first author of the study, explained: “I wanted to understand the growth of corals in my brain, so I did a CT scan.
“This data accumulated between 2018 and 2023 allowed us to estimate the production of calcium carbonate. As a result, we were able to estimate how much carbon is stored each year and prevent it from being released into the atmosphere.”
Tropical coral reefs such as Abrolhos and Fernando de Noronha have similar calcium carbonate production rates to those found in the areas studied by the authors. However, it is not yet known why Arcas corals do not accumulate to form coral reefs around the island.
Are the brain corals the source of carbon or are they drained?
This study reveals that carbon sequestration may be another important ecosystem service provided by brain corals in the Alcatrazes Archipelago. The most well-known is species protection, many of which are useful for fishing.
Calculation of carbon captured in alcatraze is the first step in understanding the role of subtropical coral reefs in the global carbon balance. Tropical corals exposed to light and warm waters can release more carbon than they absorb because the organisms that live there respiration rates.
However, the fact that they do not form large coral reefs and the rocky areas are primarily covered with macroalgae that absorb Co through photosynthesis can make subtropical environments such as alcatraze into greenhouse gas sinks, which can absorb more carbon than they release.
Additionally, corals store carbon in mineralized forms that can last for centuries or centuries. This is in contrast to the organic carbon produced by photosynthesis, which is rapidly reintegrated into the atmosphere by the respiration of living organisms and decomposition of organic matter.
Large amounts of calcium carbonate from the main island of Alcatraze
Researchers also show that in addition to brain corals, calcium carbonate is present in large quantities in sediments on the main islands of alcatraze.
Residues from the structures of other organisms, such as coral skeletal failures and mollusk shells, are deposited on the seabed and can remain there for centuries, even centuries.
“Society tends to value areas like Alcatraze, primarily because of what they protect from fishing. However, this environment may provide another important service in the context of carbon being released daily through the combustion of fossil fuels.”
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