Too small to be removed by washing machine filters or by sewage treatment plants, most of the tiny threads end up in the sea.

Sydney - More than three-quarters of the corals in the Caribbean Sea have been lost in the past 35 years and half the cover in Australia's Great Barrier Reef has died since 1960, marine scientists meeting in Cairns said on Monday.

Global warming means that most of the corals that remain would face water temperatures above their current tolerance, James Cook University Professor Terry Hughes told the 1,900 marine scientists gathered in the east coast city.

“The future of coral reefs isn't a marine version of tree hugging but a central problem for humanity,” Hughes said in a statement at the start of the five-day International Coral Reef Symposium.

The symposium, held every four years, issued a 2,600-signature statement calling for a worldwide effort to save coral reefs.

“This year, our big focus is on the Great Barrier Reef because of the location we are in,” symposium spokeswoman Jackie Marks said, “but we're also talking about ocean acidification.” - Sapa-dpa