Baby shark study reveals impacts of climate change on Great Barrier Reef species - ABC News  01/12/2021 21:16:40 

Baby sharks will find it difficult to survive on the Great Barrier Reef by the end of the century, scientists say, with climate change and warmer oceans leading to the creatures being born smaller, exhausted and undernourished.

  • The study looked at the growth of epaulette shark hatchlings in controlled settings simulating future ocean temperatures
  • It found sharks were born smaller and lacking the energy needed for their first days of life
  • Researchers are concerned about shark species not as strong and adaptable as the epaulette shark

A new study by James Cook University's (JCU) ARC Centre of Excellence for Coral Reef Studies focused on epaulette sharks, an egg-laying shark found only on the Great Barrier Reef.

Study co-author Jodie Rummer said the epaulette shark was a species that was "really tolerant" to challenging and changing conditions, including ocean acidification.

"Warmer temperatures are really having a negative effect on at least the early development of this particular shark species."

Dr Rummer and the JCU team, including lead author and PhD candidate Carolyn Wheeler, studied the shark eggs and hatchlings in controlled environments, simulating current reef temperatures and predictions for the middle and the end of the century.

She said temperatures were expected to rise from 2 to 4.5 degrees Celsius by 2100.

"We could control conditions tightly in the laboratory and isolate the effects we were seeing and associate them just with that elevated temperature effect," Dr Rummer said.

Three new born sharks cuddling up together in a tray
Rising ocean temperatures are presenting a massive problem for baby sharks.(Supplied: Conor Gervais, James Cook University)

Ms Wheeler said researchers found the warmer the conditions the faster the embryos developed.

"The embryos grew faster and used their yolk sac quicker, which is their only source of food as they develop in the egg cast," Ms Wheeler said.

"This led to them hatching earlier than usual.

'Flow-on effects for entire ecosystem'

Dr Rummer said this was a concern for the future of all species of sharks.

"If this shark is having trouble coping with ocean warming conditions, that's going to be a really big problem for other shark species that are less tolerant and not as robust to changes in their environment," she said.

"If one species in an ecosystem is impacted, it can have flow-on effects to an entire ecosystem's health.

Dr Rummer said if ocean warming did not stop, sharks would have to find new cooler habitats to live in or adapt over generations.

"[But sharks are at a] particular disadvantage for adaption as they can't change their DNA over generations fast enough to keep up with the changing planet," she said.

The study has been published on Scientific Reports.

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