Danger for dugongs and turtles as La Nina destroys food supplies

Boaties are urged to take care on Moreton Bay, as La Nina wreaks havoc on turtles and dugongs, forcing them to migrate south in search of food.

UniSC Associate Professor of Animal Ecology Kathy Townsend says seagrass beds around Hervey Bay have been wiped out by rain and floods washing large quantities of sediment out to sea, where it smothers the seagrass leaving the animals with only two choices: move away or try eating something else.

Mayor Peter Flannery says last week a turtle and a dugong washed ashore on Bribie Island, highlighting the impact of dwindling food sources.

What to do with stranded turtles

“Turtles and dugongs are the grazers of the ocean and need seagrass meadows to survive, which we usually have an abundance of in Moreton Bay, but our seagrass has also been flood damaged,” he says.

“We’re seeing more animals moving into an area where there’s less food, which means they’re weak and often nearer to the surface, unable to quickly move away from boats.

“We need boaties to keep an eye out, slow down and be safe to avoid hitting these poor animals, which are already weak and may not survive.”

Mayor Flannery says anyone who finds a stranded sea turtle should call the Queensland Parks and Wildlife Service marine stranding network on 1300 130 372.

He says turtles should not be returned to water, because it delays efforts to properly care for them.

Depleted food supplies

Associate Prof Townsend says the three major floods that engorged the Mary River and dumped huge amounts of sediment into Hervey Bay were even worse than the floods that hit Moreton Bay.

“In normal years, sediment from rivers brings a flush of nutrients, which can actually cause a seagrass boom once the water quality improves,” she says.

“The problem is there’s been just too much sediment.

“With one La Niña after another, it’s been harder for seagrass to recover or regrow.”

Associate Prof Townsend says that as sediment from the floods spread out over the shallow sea, it made the water murkier, meaning sunlight couldn’t penetrate the gloom to reach the seagrass meadows.

Despairing for dugongs

“The result has been widespread devastation in the Great Sandy Straits region,” she says.

“Summers are when our seagrass meadows usually flourish, letting turtles and dugongs fatten up for the winter. During winter, seagrass naturally dies back.

“Sea turtles in poor condition will not be able to migrate successfully, which means they’re heading for a poor nesting season.”

Associate Prof Townsend says dugongs are also struggling.

“Without stores of fat, the females won’t be able to support their calves through to weaning stage. “That will make it harder to replenish the population and recover from losses from starvation or relocation.

“We won’t know the full impact until years from now.”