While the anemones suffered from bleaching and climate change, they were able to keep producing venom, giving them an edge in surviving the long-term changes to marine environments, the scientists said in a statement.

In a paper titled The Ecological Importance of Toxicity: Sea Anemones Maintain Toxic Defence When Bleached, the scientists, from the university's Saving Nemo program — named after the well-known film — listed the deleterious effects that heatwaves and bleaching had on anemones, which are the natural home of clownfish. The paper was published in the online journal Toxins.

“The loss of symbiotic photosynthetic algae under extreme climatic conditions causes whitening in colour, loss of internal food supply and reduction in health which can ultimately lead to death,” said Professor Karen Burke da Silva, from Flinders University’s College of Science and Engineering, who leads the Saving Nemo program.

“However even under extended light-induced bleaching over five months, the sea anemone (Entacmaea quadricolor) shows remarkable resilience in maintaining venom quality and quantity to stay alive.”

But, despite the environmental challenges, the study showed that the struggling marine invertebrates fought to produce sufficient venom to maintain nematocyst production so that they could capture prey during falls in internal algae food sources during the bleaching.

“One of the most venomous animals in the world, already under significant ecological threat due to rising pressure on marine environments, seems to use its amazing venom production as a last line of defence against climate change,” said Professor Burke da Silva.

“Their resilience during times of high stress will aid in the their survival and consequently the survival of dependent anemonefish.”

It is also important for the symbiotic relationship with colourful "Nemo" clownfish which rely on anemone for protection and shelter.

The anemones used in the study are endemic along the north-eastern coast from Far North Queensland to North Solitary Island, NSW. They have a thermal tolerance threshold between 25°C and 27°C, with average summer temperatures in this region hovering around 26°C.

“This species is at risk in Australian waters, as it is within 1°C of its thermal threshold,” the researchers said.