Playing underwater sounds could help coral reefs fight global warming

2023 was the hottest year recorded on planet Earth – and that includes the world’s oceans, where records fell like dominos. Last week, around 5000 scientists gathered in New Orleans for the American Geophysical Union’s biennial Ocean Sciences Meeting. Environment reporter James Dinneen was there to take the temperature of the researchers, who have been watching change after change unfold in the seas. You can hear the segment at around 05:00 in the embedded player or read the transcript below.

Transcript

James Dinneen: There was one thing on everyone’s mind at the world’s largest gathering of ocean scientists: heat.

England: “The warming over the last couple of decades, but especially this warming in 2023, has taken over the field.”

James: Matthew England is an oceanographer at the University of New South Wales in Australia. He was one of thousands of ocean scientists gathered in New Orleans to discuss the latest research on what’s happening at sea.

There are presentations on everything from new types of octopus to robotic flying fish. But rising temperatures are stealing the show.

England: “Our burning of fossil fuels, our emissions of greenhouse gasses into the atmosphere, we know that’s trapped heat, we know that 90 plus percent of that has gone into the oceans.”

Average sea surface temperatures last year smashed the previous record, rising around 0.2 degrees Celsius above 2022 levels. The amount of heat in the top 2000 meters of ocean waters also broke records. And there were extreme marine heat waves from the Atlantic to the Sea of Japan.

England: “It was the first year in all the records where it was hard to find a part of the ocean that wasn’t warmer than average.”

Researchers here are grappling to understand the drivers and consequence of all that heat.

Take the mystery of Antarctica’s sea ice cover, which was surprisingly robust until 2016. That year, it dropped drastically. In 2022 it set another record low which was broken again in 2023 when the ice failed to recover in the Antarctic winter.

But perhaps the most unambiguous victims of 2023’s temperatures were coral reefs. Large swaths of coral bleached and died, especially around the Florida Keys in the Gulf of Mexico.

Ian Enochs at the US National Oceanic and Atmospheric Administration studies the reefs in the Keys. He says seeing so many corals die was a painful experience, but has only drove home the urgency of action.

Enochs: “Some people would look at this and be downtrodden. And I have seen the exact opposite of that I’ve seen people come together and be so motivated to actually do something meaningful, be able to face this head on.”

Take Amy Apprill at the Woods Hole Oceanographic Institution in Massachusetts, who is working on different approaches to restoring coral ecosystems. There are lots of ideas. But one new approach her team is working on would use underwater sound.

Apprill: Sound is a fundamental cue that’s used by reef organisms. We know it as a part of their communication strategy, and something that they rely on to create that healthy environment.”

In tests at a reef in the Virgin Islands, the researchers found that broadcasting recordings of a healthy reef ecosystems underwater increased the rate at which coral larvae attached to the reef. This could help make coral restoration more effective in the face of rising temperatures.

Apprill: It’s just been an unprecedented year. But the piece that I hold on to and that keeps me optimistic is we are just starting, we are just scratching the surface of putting these solutions into action.