Losing Nemo? Wider Effects Of Mass Great Barrier Reef Bleaching Emerge

Fairfax - Peter Hannam

Bleaching in the world's reefs over the past couple of years is immediately evident from the stark images of corals shedding their myriad colours for a ghostly white.
While as much as half the corals of the Great Barrier Reef died during the marine heatwaves of 2016 and 2017, researchers are only now beginning to assess the toll on the many species that rely on corals for food and shelter.
Researchers at Lizard Island on the Great Barrier Reef are studying the impacts of coral bleaching on fish and anemones that depend on them. Photo: University of Wollongong 
"A lot of the attention is on the corals," Marian Wong, a marine biologist from the University of Wollongong, said. "The public's perception is that the fish are mobile enough to just swim away."
In fact, clownfish - made famous by the Finding Nemo film  - and other species such as coral goby fish "are just terrible swimmers, designed to sit in their little spot their whole lives", she said.
Abundance of coral goby fish has dropped away markedly around Lizard Island. Photo: Catheline Froehlich
Dr Wong is part of a team of researchers who have made use of the Australian Museum's research station on Lizard Island to examine how sea anemones and fish have fared since the mass bleaching events. Where baseline data is available, early signs - at least from the far-north Queensland site - aren't pretty.
Around Lizard Island, there were about 13 species of coral gobies, a social fish often found in groups.
Now there is only a "very, very low abundance", Dr Wong said. "It's almost a complete location extinction of gobies there."
Anna Scott, a researcher from the Southern Cross University, studies sea anemones.
Clownfish are among the species hammered by the coral bleaching on the Great Barrier Reef in 2016 and 2017. Photo: University of Wollongong
These species, related to corals, also bleach when stressed by high temperatures, expelling the algae that provide them their vivid colours and much of their energy.
When anemones die, anemone fish - including clownfish - lose the protection of the stinging tentacles and become easy prey for other fish.
Marian Wong, a marine biologist at the University of Wollongong, at Lizard Island.Photo: University of Wollongong
A visit last month to Lizard Island revealed "the first signs of recovery" in anemones, Dr Scott said. Since the area had not been mapped before, the recent work will serve as a baseline for future comparisons.
"There's a decline in numbers [of anemones from the bleaching] but we don't know the scale of it," she said.
While many changes may be subtle, others are obvious even to the casual observer.
The recent visit was notable for the absence of beautiful butterfly fish - which typically swim in pairs. "I don't think I saw a single one," Dr Wong said.
Whether coral, anemones and the fish that depend on them return in numbers resembling their more recent abundance likely hinges on "whether or not they are given time [to recover] without these warming events", Dr Wong said.
"These will keep happening if we continue, business as usual, with our use of fossil fuels."


No comments :

Post a Comment

Lethal Heating is a citizens' initiative