A sprinkling of pumice is starting to arrive in Australia after a long voyage across the Southwest Pacific. The visiting volcanic raft has also brought a housewarming present to its new location in the form of millions of reef-building organisms that could benefit the Great Barrier Reef. 

The enormous field of pumice, made up of trillions of tiny seperate pumice stones, was spewed out in August 2019 by an underwater volcano found off the northwest coast of the island of Vava'u in Tonga. Pumice is formed when liquid lava erupts from a volcano into the sea and cools rapidly. It obtains its porous structure through gasses that have bubbled up through the frothy magma as it's cooling. 

At its largest extent, the floating field of pumice was estimated to be 167 square kilometers (64 square miles) in size, around double the size of Manhattan.

Scientists were aware it was heading towards Australia, but now increasingly more pieces of pumice are arriving on the beaches in southeast Queensland. Associate Professor Scott Bryan of the Queensland University of Technology has been surveying the beaches for pumice since April 2020. He hopes the pumice will restock some of Australia's coral reefs by bringing new healthy corals and other biological material that has hitched a ride on the way.

“Each piece of pumice is a home, and a vehicle for an organism, and it’s just tremendous,” Professor Bryan said in a statement. “The sheer numbers of individuals and this diversity of species is being transported thousands of kilometers in only a matter of months is really quite phenomenal.”

“Overall, we’ve identified more than 100 different species attached to the pumice – a tremendous diversity of plants and animals,” he added. 

Some scientists, however, have argued the original story of the raft became sensationalized after the media proclaimed it will “save the Great Barrier Reef.” Others are also more skeptical about the life-giving properties of the pumice raft. Dr Rebecca Albright, a coral biologist from the California Academy of Sciences, told Scientific American in 2019: “By the time the pumice reaches Australia, there is a diverse community of things living on it. But will corals be major players? No, absolutely not.”

“It could actually abrade the reef,” she added.

While Professor Bryan also believes the pumice won't be enough to save the troubled Great Barrier reef, he hopes it will at least breathe some new life into the shores of Australia. 

“It’s almost like a vitamin shot for the Great Barrier Reef,” he said. But, “Pumice rafts alone won’t help mitigate directly the effects of climate change on the Great Barrier Reef.”