89% Reproductive Failure Among GBR Coral Populations After Back-To-Back Bleachings
The amount of baby corals born on the Great Barrier Reef crashed in 2018 in what scientists are describing as the early stages of a "huge natural selection event unfolding".
They found new coral "births" dropped by 89 per cent as a direct result of back-to-back bleaching events in 2016 and 2017. And the types of corals that were able to reproduce changed too, meaning there will be long-term reorganisation of the reef ecosystem if the trend continues.
The reason there was such low birth or "recruitment" of new corals is because many of the mature breeding adults were wiped out in the bleaching events of the previous two years, and so weren't around to produce offspring. It will take the fastest-growing species a decade of bleaching-free conditions to recover their breeding populations, they report in the journal Nature today. And some of the slower-growing coral species will need 20 years or more to recover.
But severe bleaching events, which used to occur once every 25 years prior to the 1980s, now occur on average every 5.9 years, meaning it is statistically likely that another event will hit before the reef has recovered from the last.
EDIT
https://www.abc.net.au/news/science/2019-04-04/great-barrier-reef-changes-coral-bleaching-recruitment-plummets/10962054
