Scientists hope a giant pumice rock floating in the Pacific Ocean will help restore the Great Barrier Reef (Credit: NASA Earth Observatory images by Joshua Stevens, using Landsat data from the U.S. Geological Survey)

Australia’s Great Barrier Reef, home to over 1,500 fish species and countless other marine animals, is in trouble. Rising ocean temperatures, attributed to climate change, have destroyed about half of its coral since 1998. On August 30, 2019, the Great Barrier Reef Marine Park Authority downgraded the ecosystem's condition from "poor" to "very poor" and warned that the window of opportunity to save it was rapidly closing. Now, some scientists are hoping that a gigantic piece of pumice stone currently floating towards Australia will aid in the recovery of the world's largest coral reef system.

The massive sheet of stones, which stretches out 58 square miles — about the size of Washington, DC — was first spotted by Shannon Lenz on August 9, 2019. In a video posted on YouTube on August 17, 2019, (below) she wrote, "On August 9, 2019, we sailed through a pumice field for 6-8 hours, much of the time there was no visible water. It was like plowing through a field. We figured the pumice was at least 6-inches thick."

A few days later, on August 17, Michael and Larissa Hoult, an Australian couple sailing to Fiji, reported encountering "a sheet made up of pumice stones from marble to basketball size such that water was not visible," on their Facebook page. The couple later told CNN that they had been at sea for 10 days when they came in contact with what appeared to be floating gray matter. "It was quite eerie, actually," Larissa said. "The whole ocean was matte — we couldn't see the water reflection of the moon."

"The rocks were kind of closing in around us, so we couldn't see our trail or our wake at all. We could just see the edge where it went back to regular water — shiny water — at night," Michael added.

The floating sheet is believed to have been created by an underwater volcanic explosion recorded by NASA Earth Observatory satellites near Tonga — an archipelago of 176 islands in the South Pacific Ocean — in early August. As the lava rose to the ocean's surface, it cooled and hardened into a sheet of porous stones. Like icebergs, the volcanic stones can only be partially seen from the water's surface. The smaller, lighter pieces float to the surface, while the larger, heavier rocks are submerged, leaving only about 10% of the raft visible. According to NASA, while underground volcanoes often explode and emit debris, pumice rafts are rarely observed.

Michael Hoult retrieved a few pieces of the volcanic rock from the massive sheet (Credit: Michael Hoult)

The porous stones, which are being pulled towards Australia by the ocean currents at speeds of about 10 to 30 kilometers (six to 19 miles) per day, are undoubtedly fascinating to observe. However, what makes the raft invaluable to scientists is the array of organisms, ranging from crabs to corals, which reside in the tiny crevices.

Scott Bryan, a professor at the Queensland University of Technology, told The Guardian, "Each piece of pumice is ... home and a vehicle for marine organisms to attach and hitch a ride across the deep ocean to get to Australia." He is optimistic the rocks will sink around the Great Barrier Reef, forcing their inhabitants to attach themselves to the reef, allowing for entirely new colonies of coral to grow and thrive. Bryan's theory is based on a 2012 study he conducted on a similar pumice raft which proved effective in helping redistribution and diversification of ocean life.

The Great Barrier Reef, the world's largest coral reef system, is being threatened by climate change (Credit: Toby Hudson /CC BY-SA 3.0/

However, Rebecca Albright, a coral biologist and curator at San Francisco's California Academy of Sciences, does not share Bryan's optimism. The expert told Scientific American, that to restore the Great Barrier Reef, a coral polyp would have to abandon the pumice rock and move to one of the existing bleached coral branches in the reef. "There is a phenomenon called polyp bailout, where a polyp of coral leaves its skeleton and ... finds another place to set up shop. But this is a stress response and a rare, crazy thing,” Albright said.

Even if Bryan is right, the raft's ability to restore the Great Barrier Reef may be limited. A 2006 study conducted on a similar pumice stone sheet found thousands of organisms, ranging from barnacles to anemones and worms, attached to the stones. However, coral polyps — crucial to the reef's restoration — accounted for just one percent of the rock-dwellers. There is also the possibility that the ocean currents will drag the raft in a different direction so that it never reaches the Great Barrier Reef. Hence, instead of pinning their hopes on Mother Nature, humans need to take action now and save the world's largest coral reef system before it's too late.