Coral discovered in the extreme mangrove environment off of Howick Island in the Great Barrier Reef ... [+]
The Great Barrier Reef has undergone a progressive decline since the 1980s, including its worst-ever mass bleaching in 2016.
Up until now, lots of research on the Great Barrier Reef has focused on areas where extreme conditions, such as excessive heat, are dampened. Corals cannot typically withstand sudden increases in temperature, so protected 'pockets' of corals that do not receive the full effects of a heat wave could help repopulate devastated reefs nearby.
However, these 'pockets' will not be a permanent savior to Great Barrier Reef corals once the heat waves become excessive within them, too.
"...even the ‘robust reefs’ might be wiped out in the not-too-distant future – unless we really get serious right now about mitigating global warming," explains Dr. John Alroy, Professor at Macquarie University in Sydney.
This problem inspired researchers from the University of Technology Sydney in Australia to take an unconventional approach to studying the Great Barrier Reef in the face of climate change. Instead of looking for more coral 'safe havens', these scientists searched for areas already experiencing conditions more extreme than the average reef to see if there were any corals hardy enough to handle the pressure - and what they found may be great news for the future of the Great Barrier Reef.
The Woody Isles mangrove lagoon in the Great Barrier Reef Marine Park, where researchers discovered ... [+]
Researchers honed in on two mangrove lagoons that frequently experience extremely hot, acidic, and oxygen-lacking conditions - a death sentence for the average coral - and found over 30 different species of corals thriving.
"The presence of corals in these extreme mangrove habitats challenges our understanding of the conditions some corals are capable of living in," explains Dr. Emma Camp, lead author of this study. "The extreme mangrove lagoons act as a natural laboratory to allow us to study the mechanisms that support coral resilience to sub-optimal environmental conditions—predicted to become the norm for coral reefs in the future."
Dr. Camp and her collaborators took their research one step further and essentially tested the 'health' of a couple corals from one of the mangroves to better understand how these corals were withstanding these extreme conditions. Specifically, they looked at two coral health metrics: first, how fast the coral species calcified, or grew their chalky skeletons, and second, how much the corals were converting energy using respiration versus photosynthesis - an indication of how reliant the corals may be on light-converting algae cells they house.
Indeed, these corals were calcifying and converting energy differently than corals living outside the extreme mangrove environment. The calcification rate of the mangrove corals was 20-30% lower, while respiration, meaning energy conversion without the help of algae, was enhanced by up to 35%.
Coral polyps with tentacles extended for feeding (left), and banded growth patterns from coral ... [+]
These differences highlight a survival 'trade-off' required for living in this extreme mangrove environment. Although these corals can withstand the harsh environment, they are not able to grow as quickly as their less-extreme neighbors, and must rely more heavily on eating plankton to compensate for less active mutualistic algae cells.
"There is a lot we don’t know," says Camp. "For example, are these extreme corals already at their limit? Can they survive more stress if we transplant them to more stable environments? Will they maintain their stress tolerance?"
Future research hopes to tease apart the significance and capabilities of these newly discovered 'super corals'.
