The deadly back-to-back bleaching events that hammered Australia's Great Barrier Reef in 2016 and 2017 led to a collapse in the recruitment of new corals, severely affecting the ecosystem's ability to recover from the devastation.
Rosemary Steinberg, of the University of New South Wales, said the islanders need to work closely with local corporations and businesses to help make their reefs more resilient. "We used to think that the Great Barrier Reef was too big to fail - until now". Coral bleaching, which can eventually kill corals, has been reported throughout South East Asia, the Indian Ocean and the Pacific. "The reef won't disappear, but it is already transitioning rapidly to a new configuration".
Some areas within the Lord Howe Island lagoon coral reef are not showing signs of bleaching and have remained healthy and vibrant throughout the summer.
"Dead corals don't make babies." added Hughes, warning the only way for the reef to survive would be bringing down global temperatures by cutting greenhouse emissions. If not allowed to recover free of stressors, the corals can perish. After eight weeks they were collected and carefully inspected under a microscope to count the number of newly settled coral recruits.
The decline in the number of adult corals over 2016 and 2017, when global warming led to higher temperatures and mass bleaching, meant there were fewer baby corals introduced to the reef in 2018 compared to previous years.
The Great Barrier Reef (GBR) is the world's largest reef system.More news: Where Have Measles Cases Been Reported in 2019?
Warm temperatures and pollution trigger coral to expel the algae that lives in their tissues.
Some produce tiny larvae directly, others eggs and sperm in annual mass spawning events.
Several adult corals died following ocean heat waves that resulted in mass bleaching and the new corals are not able to settle in the ecosystem. However, the substantial and widespread reduction of regrowth indicates the magnitude of the disturbance caused by recent heatwaves. "We show that coral recovery rates across the GBR declined by an average of 84 percent between 1992 and 2010".
The study surveyed 100 major coral reefs, from 1980 through 2016, and found that only a handful had not suffered severe bleachings during that period.
"There is evidence that some corals are now dying on the most severely affected reefs".
This is actually what has been seen in the corals near Lord Howe Island, which is 600 km far from the shore of Sydney.More news: MIT cuts ties with Huawei and ZTE
They then compared these figures with measurements of young coral numbers in the years prior to 2016-17.
"Recovery rates because of these very low levels of recruitment are going to be much, much slower, than would have occurred otherwise", Pratchett said.
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"There's such a diverse eco-system because of that relationship between the coral and the algae that makes this lovely 3-dimensional home for all these other animals".
The only way to effectively redress global warming is to immediately and substantially reduce global carbon emissions. However, in an era of climate change, this is looking increasingly unlikely, given that extreme events-such as mass bleachings-are predicted to increase in frequency.
This article is republished from The Conversation under a Creative Commons license.More news: Google Play closing Artist Hub, Play Music to merge with YouTube Music
While further management is required to minimise more direct human pressure on coral reefs - such as sediment run-off and pollution - all these efforts will be futile if we do not address global climate change.