Coral baby numbers crash on the Great Barrier Reef: study

Coral spawning has crashed in huge numbers on the Great Barrier Reef after recent back-to-back mass bleaching events, anew study said Thursday, casting doubt on the resilience of the beleaguered natural wonder and its ability to recover.
The Great Barrier Reef, off Australia’s north-eastern coast, is the world’s largest coral system – covering an area larger than Italy -and is one of most bio-diverse ecosystems on the planet.
The reef saw two mass bleaching events in 2016 and 2017, attributed to global warming, which saw an “unprecedented loss of adult corals.”
In the aftermath, the number of new coral larvae dropped by 89 percent compared to historical levels, according to the study by Australian researchers. It was published in the journal Nature.
“Dead corals don’t make babies,” said lead author Professor Terry Hughes, Director of the ARC Centre of Excellence for Coral Reef Studies at James Cook University (JCU) in Queensland.
The study measured how many adult corals survived the extreme heat stress, and how many new corals they produced to replenish in 2018.
In some of the northern parts of Reef, closer to the equator which saw warmer waters, the number of new baby corals collapsed by as much as 95 per cent.
The study also found the composition of baby corals shifted, which will also impact the slower-than-normal recovery and their ability to cope with future bleaching events.
“The number of coral larvae that are produced each year, and where they travel to before settling on a reef, are vital components of the resilience of the Great Barrier Reef,” said co-author Andrew Baird.
“Our study shows that reef resilience is now severely compromised by global warming.”
The researchers said the extent to which the Great Barrier reef will be able to recover remains uncertain, given the projected increase in the frequency of extreme climate events in the next two decades.
The Great Barrier Reef has experienced mass bleaching events four times in the past 20 years, all attributed to global warming.
Coral bleaching occurs when a rise in sea temperature or acidification damages the microscopic algae, a living organism inside the corals that provides them with energy and gives them their vibrant bright colours.
Scientists say if current greenhouse gas emissions are not curbed,the reef is projected to bleach twice a decade from 2035 and annually after 2044.
Last month, in another study conducted in the West Pacific’s Palau archipelago, researchers found that corals need nine to 12 years to fully recover following large environmental disturbances such as mass bleaching and storm damage.
Apart from the 2016-2017 mass coral bleaching, the Great Barrier Reef is currently recovering from an ongoing outbreak of Crown-of-Thorns starfish, as well as damages from Tropical Cyclone Debbie in 2016 and disturbance due to flooding in recent months that has sent plumes of debris, sand and poor quality water to the ocean. — DPA