Presuming that higher CO2 emissions lead to global warming, it can consequently be said that coral reefs are heating up the planet.
Image Source: Terlouw et al., 2019
Image Source: Lønborg et al., 2019
In addition to emitting CO2 (and adding to global CO2 emissions), coral reef communities are “acidifying” themselves. Corals pump more CO2 into the water in which they live as they grow.
Counterintuitively, then, the rampant and ongoing “self-acidification” in coral reef communities is an indication that the reefs are healthy and thriving.
Image Source: New Scientist
Andreas Andersson of the Scripps Institution of Oceanography in San Diego, California, and his colleagues carefully monitored a coral reef in Bermuda for five years, and found that spikes in acidity were linked to increased reef growth.
“At first we were really puzzled by this,” says Andersson. “It’s completely the opposite to what we would expect in an ocean-acidification scenario.”
The researchers observed the chemistry of the water on the reef between 2007 and 2012. During that time, there were two sharp spikes in acidity – once in 2010 and again in 2011.
The team found that coral growth itself made the water more acidic as the corals sucked alkaline carbonate out of the water to build their skeletons. The corals also ate more food during these high-activity periods and pumped more CO2 into the water, increasing acidity further.
Perhaps the only way to prevent corals from acidifying the oceans, growing their carbon footprint, and heating up the planet is to foster increased incidences of coral bleaching events.
Peak bleaching decades, however, occurred in the 18th and 19th centuries.
Image Source: Kamenose and Hennige, 2018
Yes, coral reef communities pump CO2 into the atmosphere, acidify the oceans, and heat up the planet.
It’s important to emphasize, though, that just because coral reef ecosystems do it does not mean that humans should follow corals’ lead and do the same.