Pumice raft carried nutrients to the Great Barrier Reef from nearly 2,000 miles away

In 2019, an underwater volcano near Tonga created an enormous pumice raft that floated for months and eventually made its way to the coast of Australia. Here, the pumice rock has literally brought new life to the Great Barrier Reef. 

In a study from Queensland University of Technology, an international team of scientists used underwater robots to collect samples from the volcano that produced the pumice.

“It was really our first chance to go and explore the summit of this underwater volcano,” said study co-author Professor Scott Bryan.”We were able to send underwater robots down with cameras and sampling gear to collect material from the actual volcano that produced this pumice raft last year.”

“It’s allowed us to see what these volcanoes look like underwater. It’s a volcano that’s getting close to breaching the surface and will become an island in years to come.”

“We’ve been able to see how life has come back to the summit of this volcano after this eruption, and see that restoration of life.”

“One of the advantages of our trip to Tonga is that for the first time we’ve been able to collect samples from the vent, from the seafloor so soon after the eruption.”

Professor Bryan, who has been studying the impact of pumice rafts for nearly 20 years, said that at one point the raft was twice the size of Manhattan. The pumice started arriving on Australia’s shoreline by April and spread out across a long stretch of shoreline. 

The researchers collected four different types of pumice from the Tongo eruption that can be used for comparison: the pumice collected shortly after the eruption, pumice that sank right away at the eruption site, pumice that washed up in Fiji a month later, and pumice that traveled more than 3,000 kilometers to Australia.

“We don’t understand why some pumice sinks during the eruption at the location and others can float for many months and years on the world’s oceans,” said Professor Bryan. “This will help us understand the mechanisms and dynamics of these explosive eruptions and understand better why these eruptions produce potentially hazardous pumice rafts.”

According to Professor Bryan, a nutritional boost that the pumice raft has delivered to the Great Barrier Reef is part of a very ancient process in which oceans and volcanoes have transferred marine life around the Earth for hundreds of millions of years.

“This shows that the Great Barrier Reef has connections to coral reefs that are thousands of kilometers further east. In terms of the health of the Great Barrier Reef, it’s also important that these distant reefs are taken care of.”

“Each piece of pumice has its own little community that has been transported across the world’s oceans – and we have had trillions of pieces of this pumice floating out there following the eruption.”

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

Professor Bryan said that pumice rafts will not directly help to mitigate the effects of climate change on the Great Barrier Reef. “This is about a boost of new recruits, of new corals and other reef-building organisms, that happens every five years or so. It’s almost like a vitamin shot for the Great Barrier Reef.”

The study is published in the journal Frontiers in Earth Science.

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By Chrissy Sexton, Earth.com Staff Writer