What exactly are super-corals?

By Angela Heathcote | July 28, 2017

Genetically-modified corals or ‘super corals’ have received plenty of hype, but scientists say this is not the answer to coral bleaching.

THE POSSIBILITY OF preventing coral bleaching by genetically enhancing key microalgae genes to better tolerate stress from ocean warming has been calculated by scientists for several months now. 

The first component critical to ones ability to comprehend this process is the microalgae, Symbiodinium.

Symbiodinium is among the groups of microalgae known as zooxanthellae, which are harboured by coral in a symbiotic relationship during which the algae gains shelter and nutrients from the coral and in turn provides the coral with as much as  90 per cent of its energy needs. When ocean temperatures become too warm, corals expel these symbiotic algae in a stress response that leads to coral bleaching and ultimately coral death.

Since the global phenomenon of coral bleaching began destroying huge areas of the world’s reefs, scientists have been trying to understand microalgae like Symbiodinium— its diverse thermal tolerances and genetic variation —but have been held back by “incompatible genetic engineering methods” that make it difficult to analyse and understand the algae, says Rachel Levin a University of New South Wales PhD student, who authored the study Engineering Strategies to Decode and Enhance the Genomes of Coral Symbionts, published last month in the journal Frontiers in Microbiology.

“Very little is known about Symbiodinium, thus very little information is available to improve coral reef conservation efforts,” she explained. “Symbiodinium is very biologically unusual, which has made it incompatible with well-established genetic engineering methods.”

Rachel’s study will provide a map of how to go about genetically engineering Symbiodinium, which could be used to slow-down coral bleaching by creating ‘super-algae’ and ultimately ‘super-corals.’  

However, it’s important to note that generally ‘super-corals’ refers to both genetically enhanced coral or a coral that can naturally tolerant extreme conditions.

Emma Camp, a coral expert from the University of Technology Sydney said that while the findings in the paper are encouraging, there’s still a long way to go in genetically modifying corals to make them ‘super.’

“Extensive laboratory testing would be needed to assess how achievable this is, and also whether non-native Symbiodinium can be accepted by the coral host,” Emma told Australian Geographic. “Many corals only associate with certain Symbiodinium, so getting the host coral to up-take a genetically engineered Symbiodinium could be challenging.

“We know that shifting from less stress tolerant Symbiodinium to more stress tolerant Symbiodinium can negatively impact traits such as growth and fecundity of the coral; thus, these cost-benefit trade-offs would have to be considered.”

Emma recently embarked on an expedition to find coral populations that have naturally adapted to survive under environmental extremes, including warm temperatures.

“We are currently looking at the Symbiodinium species that associate with our extreme mangrove coral populations to understand which species have adapted to survive under such extreme environmental conditions,” Emma explained.

This information could be used by researchers such as Rachel and her team to add to the list of genes that could be targeted to enhance stress tolerance in Symbiodinium through genetic engineering.

Emma argued that a combination of natural and man-made solutions will be needed to help preserve the world’s coral reefs. However, she explained, caution must be taken as both the work exploring extreme systems for stress tolerant corals and the genetic engineering route, are not a solution to coral bleaching.

“The source of the problem which is the emissions of carbon dioxide that are leading to warming sea surfaces temperatures has to be addressed if scientists stand a chance of saving the Great Barrier Reef, and other coral reefs worldwide,” Emma stressed.