See full version: The Best Way to Save Dying Coral Reefs: Bring Out the Loudspeakers
As atmospheric temperatures rise, the ocean absorbs that heat, temperatures in the sea rise, and the water becomes more acidic. Many corals are specially adapted to live in certain water temperatures; the high heat and low acidity can stress them out and kill them. In 2016 and 2017, a series of extreme heat waves killed half of the coral reefs that line Australia’s sweeping east coast.
Coral reefs around the world are one of climate change’s many casualties.
A novel new plan introduced by a team of scientists from Britain and Australia takes a different tack entirely, and relies on seemingly old school technology: loudspeakers. The scientists installed loudspeakers along a dying portion of the Great Barrier Reef and played the sounds of a healthy reef—chomping fish, scuttling shrimp, and other reef-going critters—for six weeks, in an attempt to attract more fish. here
Twice as many fish found their way back to the tune-bumping reefs than quiet ones, according to a new paper published in the journal Nature Communications. “Juvenile fish home in on these sounds when they’re looking for a place to settle,” marine biologist and study author Stephen D. Simpson of the University of Exeter said in a statement. here
The reef system in the Keys has been hit hard by climate change and disease, which is especially tough, because corals there help support fisheries worth an estimated $100 million every year. In addition, corals off Florida’s coasts are polluted by agricultural and sewage runoff. here
An estimated 4,000 fish species, and some 25 percent of marine life, depend on coral reefs at some point in their existence. Fish keep the algae that grow on corals in check, allowing corals to breathe and access sunlight. While an MPA won’t protect corals from heat waves, these natural safe zones can keep fisheries more sustainable in the long term, and fishers around well-managed MPAs often benefit from the “spillover” of healthy fish stocks that populate surrounding waters. more
Scientists often compare coral reefs to underwater rainforests, yet unlike the leafy plant base of a forest, corals are animals. The soft polyps inside the hard parts of corals are naturally translucent and get their famously vibrant color from algae living inside them.
Without a mix of long-term cuts in emissions and short-term innovation, there’s a not-so-far-off future where coral reefs as we know them simply cease to exist, says Anne Cohen, a coral expert at the Woods Hole Oceanographic Institution in Massachusetts.
The world’s coral reefs do more for the planet than provide underwater beauty.
It took several months for them to become settled in their new environments, but after that, both appeared to keep their heat-resistant properties in lab tests. And because a coral is home to thousands of genetically identical organisms, it’s likely that as the transplant grows, it will make the entire section of reef more heat tolerant.
The global outlook for coral doesn’t look good. The reef-building animals, which create the living architecture for some of the most diverse ecosystems on the planet, are acutely vulnerable to climate change, and are experiencing heavy losses already. Without dramatic emissions reductions in the coming decade, their future is increasingly dire.
More surprisingly, bleaching was also associated with an overabundance of sea urchins. Under normal circumstances, those urchins would feed on the seaweed. But when their predators are overfished, the urchin population can also explode. more
More obviously, reducing nutrient pollution (often by cleaning up sewage), could both help reefs and human health. here
The reefs that fared the worst after bleaching events tended to have an overabundance of seaweed, which flourishes in water polluted with nutrient-rich runoff, and which would normally be kept in check by herbivorous reef fish. That seaweed releases chemicals that directly stress the reef.
According to Donovan’s research, published last week in Science, those bleaching events could be exacerbated by two key local trends: pollution and overfishing. And that means that local restoration efforts could help reefs survive the majority of heat waves.
The team of scientists, co-directed by Joanie Kleypas, a scientist at the U.S. National Center for Atmospheric Research, and oceanographer Jean-Pierre Gattuso of the National Center for Scientific Research (France) and comprised of members of the Pew Marine Fellows Program and the Ocean Solutions Initiative, modelled future reef changes for two CO2 emission scenarios: the worst case and a scenario acceptable under the Paris Agreement. The former would lead to near extinction of reefs in 30 to 50 years, while the latter would give some corals time to adapt. [links]
While affected corals may recover if a period of raised temperature is brief, prolonged elevated temperature exposure can kill corals and the ecosystems they support. Many affected coral reefs that exhibited 70–80% live coral cover in the 1970s, presently exhibit less than 5–10%. more
“Coral reefs worldwide are threatened but not doomed. We have a window of opportunity to act to protect these precious and amazing ecosystems, and the ultimate outcome is entirely up to us,” said Richmond, who is also the director of the Kewalo Marine Laboratory at UH Mānoa’s School of Ocean and Earth Science and Technology.
Of the 16 possible actions for limiting the decline of coral reefs presented in the scientific literature, a massive energy transition away from greenhouse gas-emitting, petroleum-based fuels is the most effective and the only plausible one on the global scale. Actions that may be taken on regional and local levels—for example, integrated land-use practices, pollution abatement, the designation of marine protected areas and reef restoration efforts using selected genotypes or species best suited to new environmental conditions—may increase the adaptation potential of corals and the persistence of coral reefs. [links]
Coral reefs could be almost extinct in 30 to 50 years, under the worst-case scenario, according to an international group of scientific experts, including University of Hawaiʻi at Mānoa research professor Robert H. Richmond, who identified and discussed the requirements for coral reef survival in an article in Biological Conservation.