Breeding baby corals for warmer seas

March 26, 2019 by Dr Nerissa Hannink, University of Melbourne

A unique collection of baby corals has just begun to grow under the waves of the Coral Sea.

Hoping to give mother nature a helping hand, researchers have bred the corals to make them better able to cope with our changing climate – rising sea temperatures and increased acidity.

They are now growing in experimental field conditions on the Great Barrier Reef, to see if they can also thrive in the wild.

Professor Madeleine van Oppen, an Australian Research Council Laureate Fellow at the University of Melbourne and the Australian Institute of Marine Science (AIMS), is leading the project.

"Most corals in the wild are living at the very top of their survival limit in terms of temperature," Professor van Oppen says.

"The Great Barrier Reef lost half its coral cover during the back-to-back heat-induced mass bleaching events of 2016 and 2017."

She notes that the Great Barrier Reef has warmed by around 0.6 °C since the 1950s, contributing to more extreme and frequent marine heatwaves.

"Without a curb on greenhouse gas emissions, tropical sea temperatures are predicted to rise by 2-3°C by the end of the century compared to pre-industrial times. So it is vital we help corals adapt," Professor van Oppen says.

During summer heatwaves, corals become stressed and lose the microalgae that normally reside inside them in a mutually beneficial, or symbiotic, relationship. Corals receive most of their nutrition from the algae, so without them they starve and often die, turning white – coral bleaching.

Climate change also means that oceans absorb more carbon dioxide from the atmosphere, which makes seawater more acidic. When combined with rising temperatures, increased acidity can make coral more sensitive to bleaching – making it more difficult for them to form their calcium skeletons.

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