Giant pumice raft could bring new life to the Great Barrier Reef

A giant mass of pumice rocks are currently floating across the Pacific Ocean from Tonga to Australia following a deep-sea volcanic eruption. The 150km squared ‘life raft’ could bring some much needed support to the Great Barrier Reef as marine animals, including new corals, hitch a ride.

raft from space
The pumice raft seen from space covers a 150km squared area


On 16th August sailing enthusiasts Michael Hoult and Larissa Brill made a startling discovery when their catamaran was brought to a standstill on route to Fiji. The culprit? A massive raft of pumice stones stretching as far as they could see. The city-sized pumice raft is believed to be made up of trillions of rocks created when a previously undiscovered deep-sea volcano erupted in Tonga. The raft is now slowly moving towards Australia where experts believe it will end up in the Great Barrier Reef. But fear not. Scientists actually believe that the pumice raft will benefit and even rejuvenate the reef as millions of animals, including healthy corals, will attach themselves to the volcanic rock. This new abundance of marine life could settle on the reef and help it recover from the damage it has sustained from coral bleaching.

Eruption on the seafloor

When you think of a volcano erupting the image that probably jumps to mind is a rocky mountain spewing lava and smoke up into the air like a colossal chimney. But whilst you may only be able to experience this sight for yourself on land the same thing also happens thousands of metres below the surface of our oceans. The difference is that rather than erupting into the atmosphere, underwater volcanoes pump their lava and gas into the icy cold waters of our deep oceans. This causes the molten rock to solidify into hard clumps filled bubbles of volcanic gas such as carbon dioxide and sulphur. The result is a lightweight greyish rock known as pumice that is so buoyant it floats to the ocean surface. That is exactly what happened last month when a previously undiscovered volcano off the coast of Tonga violently erupted throwing tonnes of pumice towards the surface. The eruption started on 7th August and was so powerful it could be seen in satellite images from space.

Pumice as far as the eye can see

The resulting pumice raft made of trillions of pieces of rock, ranging from marble to basketball sized, stretched over the equivalent area of Manhattan. It was first discovered by sailing couple Michael Hoult and Larissa Brill as they made their way to Fiji. They described it as “a total rock rubble slick” that “went as far as we could see in the moonlight and with our spotlight”. After freeing their catamaran from the rocks they sent out warnings to other sailors to avoid the area. They were also able to take images of the pumice that went viral as they were picked up major news outlets across the world. Satellite imagery of the reef showed that it could be on course to reach Australia over the next several months. This got many people fearing for the Great Barrier Reef which has already suffered greatly at the hands of rising sea temperatures in recent years. However researchers soon realised that this pumice raft could actually be a blessing in disguise.


Journey to the Great Barrier Reef

The pumice raft has now split in half into two equally sized masses, but still remains on course to hit the Great Barrier Reef in the next 7-10 months. This means that it is on the optimal trajectory to pick up some very valuable hitchhikers on the way. That is because as it slowly moves across the Pacific past New Caledonia, Vanuatu and other coral reef abundant areas it will coincide with coral spawning. During this time millions of coral polyps will be created by the mixing of sperm and eggs in the water and take up refuge at the ocean’s surface. There they will encounter the pumice raft and rather than settling on the ocean floor will attach themselves to the volcanic rocks. There they will start to develop and by the time they reach the Great Barrier Reef they will be able to quickly integrate into the reefs coral framework. But corals aren’t the only passengers that will journey across the Pacific with the pumice raft. Algae, barnacles, crabs, snails and worms will also tag along.

new life
A piece of pumice rock washed ashore with multiple hitchhikers

Nature’s ‘life raft’

The Great Barrier Reef is currently in serious trouble as rising ocean temperatures have caused large area to be affected by coral bleaching. It is now believed that as many as half of the corals there have been lost with the highest proportion in the North. So how will these new animals change its grim outlook? Scott Bryan from Queensland University, who has spent 20 years studying this phenomenon, believes that the pumice raft will ‘restock’ the reef. He explained to The Guardian that “Each piece of pumice is a rafting vehicle. It’s a home and a vehicle for marine organisms to attach and hitch a ride across the deep ocean to get to Australia.” Not only will new corals fill the void left by dead ones but the other animals will also increase the health of the reef. It has been shown that healthy reefs with high biodiversity are a more resilient to coral bleaching. So all these millions of animals will all be very welcomed by the reef.

bleached corals
An area of bleached corals on a lifeless patch the Great Barrier Reef

It is important to note that this is not a full drawn conclusion. Whilst the raft is on track to reach the Great Barrier Reef it could still be knocked off course by storms or broken up into even smaller pieces. If it moves faster or slower than predicted it may also miss picking up the vital corals that the reef so desperately needs. However if experts are correct it will be a much needed boost to the world’s largest reef system. It is not a long term fix or a reason to stop worrying about the reef but it could buy some valuable time. It also inspires hope that nature is able to heal itself in this way. It is incredible to think that a deep-sea volcano hundreds of miles away could create a way of moving millions of animals across the open ocean at the benefit of a dying ecosystem. It highlights to me that the battle to save our oceans is far from over.

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