Coral reefs may date back to the age of dinosaurs, up to 160 million years ago, and are likely to have survived previous episodes of global warming, international research suggests.
Tropical reefs do still face an "existential threat" from man-induced climate change but their partnership with algae may have helped them to survive previous major climate events, the study published in scientific journal Current Biology says.
Research led by Dr Christian Voolstra, of the King Abdullah University of Science and Technology in Saudi Arabia, indicates that "modern" corals and their algal partners have been "entwined with each other" for 160 million years.
This is 100 million years earlier than previously thought, according to Dr Voolstra, associate marine science professor at the university’s Red Sea Research Centre.
“During their long existence, they have faced severe episodes of environmental change, but thanks to their biological characteristics have managed to bounce back after each,” he says.
Micro-algae, also known as zooxanthellae, live inside the cells of corals, allowing them to acquire energy from sunlight and to build the “massive, economically valuable reef formations upon which countless marine organisms rely for habitat”, the study says.
The team used genetic evidence, including DNA sequences and genome comparisons, to calculate the micro-algae’s approximate age of origin.
Dr Voolstra emphasised that discoveries like this did not change the fact that coral reefs were under threat from climate change but he said the information would improve conservation efforts.
Corals in Ireland
Irish specialists Prof Louise Allcock of NUI Galway and Dr Aaron Lim of University College Cork noted that the formations with this type of micro-algae off the Irish coast are limited to a few shallow water species of cup corals.
Cold water corals found in water depths of 600 to 1,600m are too far from sunlight for algae to survive, Prof Allcock explains.
“Lophelia reefs are probably tens of thousands of years old so won’t have experienced high CO2 regimes,”she says, but the families containing many reef building species could be up to 160 million years old.
“Our deep-water corals are still potentially vulnerable to climate change as the associated acidification of oceans makes it harder for them to form the carbonate required for their skeletons,”she says.
“It’s true that corals have survived periods in the past with high CO2 levels, but never have they had to cope with such a rapidly changing ocean which gives them little time to evolve.”
The cold water coral carbonate mounds which deepwater corals form here can be up to 100m tall, and can be up to 2.6 million years old, Dr Lim says.
“When conditions are favourable, the cold water corals grow, trap sediment and this helps to generate a mound feature. However, this isn’t constant. Over the past 2.6 million years there have been a number of shifts in the climate which have influenced when mound growth has been active or inactive,”he says.
“As for how they will pan out under modern environmental change, we are still unsure. However, work that we have recently carried out on one of these mounds shows that there have been clear signs of change.”
