Two cyclones and as many bleaching events have hit parts of the Great Barrier Reef in the past three years. UOW researcher Dr Marian Wong tells Agron Latifi this has been devastating for coral and fish.
“The reef may never be the same ever again, we may have a reef but it's not going to be like the one I remember.”
So says marine biologist Dr Marian Wong from the University of Wollongong’s Centre for Sustainable Ecosystems Solutions.
Dr Wong’s comments follow her latest visit to the Australian Museum’s Research Station on Lizard Island, located in the far northern sector of the Great Barrier Reef, around 240km north of Cairns.
She found that a large majority of the once colourful coral surrounding Lizard Island had now turned a ghastly brown.
Dr Wong was at Lizard Island as part of a team of researchers from UOW, Southern Cross University and The University of Technology Sydney, looking at the behavioural patterns of, and the effects of coral bleaching on species of anemone fish and goby fish that live within the anemones and coral.
Their research looked into the huge death of coral around Lizard Island and the effects on those fish that depend closely on hard and soft coral.
“Most people know anemone fish thanks to the movie Finding Nemo. But not a lot of people know that ‘Nemo’ fish are having a tough time due to the Great Barrier Reef bleaching events,” Dr Wong said.
“Clownfish, in turn, use the anemones as shelter to lay their eggs and raise their young.
“Lose sea anemones and you could say that Nemo may be left homeless.”
Lose sea anemones and you could say that Nemo may be left homeless.
But clownfish are not the only reef dwellers in danger.
Goby fish are also having a hard time.
These inch-long brightly coloured fish enjoy removing toxic algae from coral. But, as the coral bleaches and then eventually dies, the goby fish have nowhere left to live.
Coral bleaching is a global problem that researchers all over the world are trying to mitigate.
It is caused when the temperature of the ocean rises above normal for an extended period of time.
Over the last three years coral bleaching has led to a widespread coral decline and habitat loss in the northern part of the Great Barrier Reef.
It is in stark evidence at Lizard Island, labeled the “ground zero” for two mass bleaching events which have killed an estimated 29 per cent of shallow water coral reef-wide, according to findings by the Great Barrier Reef Marine Park Authority.
In December 2015, the Great Barrier Reef was exposed to above average sea surface temperatures, due to the effects of climate change.
Then in the late summer of 2016 a mass coral bleaching led to another loss of shallow water coral.
Winter sea surface temperatures in 2016 remained above average and, by the beginning of 2017 the accumulated heat stress on the reef resulted in a second wave of mass bleachings.
“There are still patches of colour, but so many corals are dead now with algae growing over their skeletons,” Dr Wong said.
But she said widespread coral decline could be recovered over time.
“Corals can recover. But it takes time, perhaps many years before they grow back to a size that is large enough for coral gobies.”
Dr Wong, a self-confessed fish lover has visited the Australian Museum’s Lizard Island Research Station (LIRS) since 2003.
“With the huge death of corals around Lizard Island the effects on those fish that depend closely on coral is really worrying,” she said.
“Many marine animals rely on coral reefs for habitat and food. Severe coral bleaching undoubtedly has an impact on marine life like the goby fish.
‘’The big question is: how long it will take for the reef to recover from ocean temperature rises?”
Current trends in ocean temperature and future predictions suggest bleaching could occur each year within the coming decades.
Some reefs around the world have experienced consecutive years of bleaching, with barely any opportunity for colonies, let alone reefs, to recover.
Dr Lyle Vail, director of the Lizard Island Research Station, said the majority of the flat reef surrounding the island has been hammered by warming temperatures and cyclones over the past three years.
“The category four cyclones Ita and Nathan in 2014 and 2015 stripped out all but the most robust corals. But it was nothing compared to the extensive coral bleaching in 2016,” Dr Vail said.
The area most severely affected by the cyclones and the bleaching event was the formerly pristine northern third of the Great Barrier Reef.
An average of 67 per cent of shallow-water corals died, according to a large-scale survey by the ARC Centre of Excellence for Coral Reef Studies.
“In summer a lot of that hot water on top of the reef is just staying there and cooking the coral. Around Lizard Island has been badly affected. An estimate of at least 90 per cent of the iconic acroporid corals has died,” Dr Vail said.
Ocean warming threatens the structure and function of coral reefs worldwide.
He said there was no longer any shadow of a doubt about the impacts of global warming in relation to our reefs...and the cause of coral bleaching was well known to scientists.
Dr Wong said the latest research project reiterated that the previous bleaching events were devastating for coral goby populations, and likely for anemone and anemonefish populations too.
“But we learnt that corals can recover because we were seeing lots of small corals reappearing and we were finding anemones and anemonefishes on the reefs,” she said. “We learnt the importance of long-term monitoring of these fishes so we can track and predict their population sizes following any further bleaching events.”
Now researchers are looking at new studies that deal with its effects on the structure of communities of hundreds of species of reef-colonizing fish.
University of Wollongong PhD student Siobhan Heatwole, who is studying the social behaviour of habitat in reef fish, is taking a deeper look at the behaviours of anemone fish.
The young biologist, who was on her eighth trip to Lizard Island, said she was particularly interested in clownfish and whether they show any behaviourial traits in relation to their changing environment.
The most significant impacts of climate change on clownfish are those affecting their coral reef habitat, water temperature and chemistry.
“One of the key behaviours we are looking at is the measurement of boldness and shyness. And are clownfish more fearless on bleached coral reefs,” Ms Heatwole said.
But Dr Wong says it is highly unlikely that reefs will be granted enough respite to get the decades they need to recover, especially with the frequency of bleaching events forecast to increase.