A new study released this week has revealed that some species of corals are able to combat the effects of ocean acidification by controlling their own chemistry.
Researchers from the ARC Centre of Excellence for Coral Reef Studies (Coral CoE) at The University of Western Australia (UWA) have identified marine species that are resilient to ocean changes, which will help better understand how to protect coral reefs in the future.
Coral reef systems across the globe are under extreme threat from the effects of climate change, with rising sea temperatures and ocean acidification being two of the primary impacts on the health of coral organisms.
Lead author Dr Thomas DeCarlo said rising carbon dioxide (CO2) levels in the atmosphere were reflected in the ocean, which leads to ocean acidification.
“Acidification hampers the ability of the coral to form skeletons and shells which are the building blocks of reefs,” Dr DeCarlo said.
“In the past few decades, hundreds of experiments have shown that corals have a highly diverse response to ocean acidification depending on the species. However, the reasons why some are more tolerant than others are not clearly understood.
For their study, Dr DeCarlo and his team developed a new method to understand the internal chemistry of corals by using specialised equipment that measures the characteristics of the molecules in coral.
The team’s results showed that some coral genera show resistance to declines in seawater pH, potentially achieved by modulating the chemistry of the fluid where calcification occurs.
“The method showed corals with the most resistance are tolerant because of the way they are able to regulate their calcium levels,” Dr DeCarlo said. “This technique means scientists can identify species that are relatively resistant to ocean acidification.”
“However, we are also looking at the costs associated with resisting acidification, which may potentially make acidification-resistant corals more vulnerable to other stressors.”
Co-author Professor Malcolm McCulloch said previous studies found that even the more hardy coral species lose their ability to adapt to ocean acidification when they bleach under extreme heat events, as experienced in 2016.
“When a coral bleaches, it expels its ‘powerhouse’ — zooxanthellae symbionts, and loses the energy needed to keep its internal mechanisms running,” he said. “The longer corals stay bleached, the less likely they are to recover.”
DeCarlo, T.M., Comeau, S., Cornwall, C.E., and McCulloch, M.T. (2018), Coral resistance to ocean acidification linked to increased calcium at the site of calcification. Proc. R. Soc. B 20180564. DOI: http://dx.doi.org/10.1098/rspb.2018.0564