Category: Hakai Magazine

Can a Cold Water Bath Save the Great Barrier Reef?

In early 2020, Australia was in the grip of its second hottest summer on record. As catastrophic bush fires turned the sky black, sea temperatures on the Great Barrier Reef soared above 29 °C, causing more than a quarter of the corals on the reef to turn a ghostly white. It was the third mass coral bleaching event to hit the UNESCO World Heritage Site in just five years.

In light of the ever-increasing concentration of carbon dioxide in the atmosphere and rising ocean temperatures, scientists are scrambling to find ways to halt the reef’s rapid decline, from artificially brightening clouds to reflect more sunlight, to bolstering coral populations using in vitro fertilization.

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Overheated reefs are caught in a vicious carbon cycle

Ohad Peleg spent his childhood snorkeling among lush seaweed forests in the cool Mediterranean Sea off the Israeli coast. When he dives there today, though, he sees a barren seascape overrun by tropical invaders, from seaweed-eating rabbitfish to plumes of red calcifying algae. This is tropicalization in action. The phenomenon, in which flora and fauna from warm climates move into cooler regions that have endured heatwaves, is exemplified by tropical sea urchins decimating kelp forests in Tasmania and coral reef fish finding a permanent home in southern Japan.

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Stopping marine roadkill

When Vanessa Pirotta is surveying whales in the frigid water off Antarctica, the traffic-packed roads back home are far from her mind. “You see absolutely nothing out there at times,” says Pirotta, a marine biologist at Macquarie University in Sydney, Australia. “So when a ship eventually comes along, I think about how jarring it must be for a whale or shark.” Marine roads are invisible, but they are busier than ever. Each year, ships use these paths to ferry more than 10 billion tonnes of goods from one country to the next. Global trade relies heavily on seaborne transport, but large whales and sharks are paying the price.

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Seagrass safeguards human history

From storing carbon to guarding against ocean acidification, seagrass is fundamental to keeping ocean ecosystems in balance. But new research shows that seagrass meadows play another crucial, if overlooked, role: protecting shipwrecks and other underwater historical heritage. Ancient weapons, prehistoric fishing tools, and textiles are just some of the items scientists have discovered buried beneath the protective cover of seagrass, says Oscar Serrano, a marine ecologist at Edith Cowan University in Australia. Until now, Serrano says, no one has investigated the cultural value of seagrass meadows, which “play an important role in revealing clues about the human past.”

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150 years of shifting global fishing

For thousands of years, seafood has sustained communities, livelihoods, and economies across the world. In ancient Rome, wealthy entrepreneurs snapped up beachfront property and built elaborate fish farms. In 15th-century Chile, coastal people bartered shellfish for inland resources. The Vikings living on Norway’s Lofoten Islands were fierce and powerful raiders, but they were also prodigious fishers of Atlantic cod. Over millennia, shifts in politics and changing technology have drastically altered when and where people go to fish. But accurate scientific records of this vast history of fishing activity capture, at best, a tiny sliver of the whole.

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We have unrealistic beauty standards for coral, too

Vibrant images of coral reefs are popular features in glossy travel magazines. This spiraling kaleidoscope of neon corals leads many to believe that “pretty” must also mean “healthy.” But according to Julie Vercelloni, a marine scientist at the University of Queensland in Australia, something more sinister is often at play when corals turn a fluorescent shade.

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