Mystery surge of turtle deaths in protected Australian waters

2 hours ago 2

Dozens of green turtles have died and been washed ashore near Brisbane in the past six weeks, in a mysterious spate of strandings putting pressure on a vulnerable species.

In the Moreton Bay area, from Deception Bay across Redcliffe Peninsula and down to Sandgate, volunteers have found 19 dead turtles since the start of October, of which only two were alive and sent to Australia Zoo for rehabilitation. On Bribie Island, dozens of dead green turtles and one dead dugong have been washed ashore.

Dozens of turtles have been washed up dead in Moreton Bay and Bribie Island.

Members of the public report strandings via the QWildlife app to the state government, which then loops in volunteer groups. It can take a few months for the information to be validated and added to the public database.

Queensland Conservation Council ecologist Natalie Frost said the two groups were reporting a surge compared with previous years, and it could not be explained without funding for scientists or vets to perform necropsies. At present, the turtles are simply photographed and then buried – the small ones by volunteers, and the large ones by the council.

“The issue has been around just not understanding exactly the cause of death for a lot of them – there are seemingly healthy turtles that have been washed ashore,” Frost said.

Among the Moreton Bay turtles, seven of the 19 were sick, skeletal or covered in algae or barnacles, four were hurt in a boat strike, two were entangled in crab pots, and the others had no obvious illness or injury. Turtles are more likely to be hit by a boat if they are malnourished or ill, including “floating syndrome” – a gas build-up often from eating plastic that makes the animals overly buoyant.

Frost called for the Queensland government to take the lead in investigating the cause of the deaths and coming up with a plan, while the federal government needed to pass stronger nature laws to protect turtles and their habitat.

Green turtles, which are under pressure because of climate change and urban development, are protected under federal environmental laws, and one of the species is the target of a national recovery plan for marine turtles. The area around Deception Bay and Bribie Island is mostly protected by the Moreton Bay Marine Park.

Associate Professor Kathy Townsend at the University of the Sunshine Coast said some mortality was not uncommon this time of year – if turtles did not end summer with good body condition, they could be malnourished and immunocompromised by the end of winter.

However, necropsies were necessary to determine cause of death and help manage threats, she said. For example, no one knew that marine plastic was so lethal until scientists inspected the insides of dead turtles.

One problem in Moreton Bay and also further north in Harvey Bay, Townsend said, was the huge amount of sediment carried by floods over the past few years, which smothered the seagrass meadows that green turtles graze upon. Dugongs also use seagrass meadows for feeding, shelter and breeding.

“As we go further in climate change, these big storm events are going to be happening more frequently and definitely being more severe as we go into the future,” Townsend said. “This increasing storm activity includes erosion of beaches where the animals would have been laying their eggs and disruption to their food supply.”

Climate change also disrupted the reptiles’ body temperatures and made it more likely that they would produce female eggs, she added.

A spokesperson for Environment Minister Murray Watt said his department was monitoring the situation and working with the Queensland government.

The Queensland Department of the Environment, Tourism, Science and Innovation was contacted for comment.

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