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China science

On ancient seabed off China’s coast, clues to how sponges can thrive after catastrophe wipes out all else

PUBLISHED : Monday, 13 February, 2017, 12:03am
UPDATED : Monday, 12 June, 2017, 12:53pm

The only life forms hardy enough to survive Armageddon, as the old joke goes, will be cockroaches and Keith Richards. But you can add sponges to the list, according to a team of Chinese and British researchers.

Not only would they persevere, according to a new study, but they would probably find post cataclysmic conditions ideal and thrive.

The theory is based on research the team of palaeontologists carried out at a well preserved fossil site known as the Anji site, on a seabed off the coast of Zhejiang province that originated 444 million years ago, the tail end of what’s known as the Ordovician period, when the planet underwent a mass extinction event that killed off 85 per cent of marine species. But the sponges did “surprisingly” well, the researchers say.

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“The sponges are often large and structurally complex, and their diversity is equivalent to the total known modern sponge diversity in the richest areas of the Southern Ocean,” the researchers from the Chinese Academy of Sciences and National Museum Wales wrote in a paper published last week in Current Biology.

They found fossils of other animals, including a sea scorpion complete with legs, but sponges were far more prevalent, with thousands of specimens found. “We think the sponges thrived because they can tolerate changes in temperature and low oxygen levels, while their food source [organic particles in the water] would have been increased enormously by the death and destruction all around them,” said Dr Joe Botting, an author of the paper, in a press release.

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During the Ordovician period, most of the world’s land mass was collected into the supercontinent known as Gondwana, which over millions of years was steadily moving towards the South Pole. Everything north of the equator was submerged in ocean, making marine biodiversity the dominant life form.

But when Gondwana finally settled at the South Pole, huge glaciers formed, sucking up water and sending the sea levels plummeting.

Extreme temperature spikes tipped the balance of chemical compositions and disrupted circulation in the ocean

“It is possible that the conditions of ecological collapse increase the particulate food sources for sponges, while they themselves are relatively unaffected by the crisis,” the researchers explained.