WWF-Australia today released video and stills which show coral spawning at Lizard Island this year has been reduced by coral bleaching.
“First the bleaching killed much of Lizard Island’s coral and now many remaining corals have struggled to spawn this year,” said WWF-Australia spokesperson Richard Leck.
“The science tells us that bleaching takes a toll on surviving corals impacting their fertility,” he said.
The worst coral bleaching event in the Great Barrier Reef’s recorded history killed an estimated 22% of the coral this year, with the mortality rate much higher in the Far North. Each year corals synchronise the release of trillions of eggs and sperm. It’s been described as “like an underwater snow storm” and “the greatest underwater sex show on the planet”. The baby coral polyps created during the spawning event drift to the bottom and take hold helping a reef to grow or rebuild.
But at Lizard Island this year the underwater snow storm failed to appear.
“Rather than there being a plentiful supply of baby corals being produced, to take the place of those lost to bleaching, at Lizard Island it looks nothing like a normal year, and that is really concerning.
“This is more evidence of the impact of climate change and shows we must redouble our efforts to fully implement the rescue measures in the Reef 2050 Plan,” Mr Leck said.
Dr Lyle Vail, director of the Australian Museum’s Lizard Island Research Station, said: “The relatively low level of coral spawn seen in the water this year is not surprising given the high mortality of corals in the northern part of the Great Barrier Reef earlier this year.
“We need to get serious about reducing our carbon footprint if we want to give future generations the opportunity to enjoy the Great Barrier Reef,” he said.
Scientists will be monitoring the effect of bleaching on the fertility of surviving corals at Lizard Island and at other locations in order to increase their understanding of the impacts of bleaching events.
Following the 1998 mass coral bleaching on the Great Barrier Reef, scientists studied the impact on two species of Acropora coral at Pelorus Island. Coral mortality was high and many of the surviving colonies did not produce eggs. The combined impact of these factors was dramatic. Assuming all the colonies would have survived if the bleaching had not occurred there was a 94% reduction in the number of Acropora hyacinthus colonies carrying ripe eggs and a 37% reduction in Acropora millepora carrying ripe eggs.
Another study indicates this drop in ripe eggs significantly reduces the rate at which drifting coral larvae attach and establish themselves on a reef.
In research published this year, scientists studied mushroom coral (Fungia scutaria) and rice coral (Montipora capitate) in Hawaii during the bleaching in 2014 and 2015 and found the volume and quality of eggs - and particularly the quality of sperm - was reduced. Eggs were surrounded by mucus and debris, something not seen in non-bleaching years. The percentage of coral sperm that swam normally was reduced by up to 47% compared to previous years.
WWF-Australia Media Contact: Mark Symons, Senior Media Officer, 0400 985 571, firstname.lastname@example.org