Underwater soundscapes and probiotics deployed as record El Nino threatens global coral reefs

Scientists are using underwater speakers to play the sounds of healthy reefs in the Caribbean Sea to help coral larvae find a home and recover from severe heat stress. Researchers at the Woods Hole Oceanographic Institution in Massachusetts broadcast recordings of snapping prawn clicks and fish thrums to lure floating larvae onto degraded reefs. This method relies on the discovery that coral larvae can sense sound and use it as a cue when searching for a permanent place to settle.

Emergency Measures

In addition to these acoustic lullabies, scientists are moving corals from shallow spots to deeper, cooler water and treating them with protective microorganisms. These urgent steps come as ocean temperatures surge due to human-caused climate change and a super-strong El Nino brewing in the Pacific Ocean. As of late August, coral bleaching had appeared in areas around Florida, the Pacific coast of Panama, and Kiribati. Elevated water temperatures strip corals of the symbiotic algae they need for nutrients, which can ultimately kill them.

Mounting Pressures

Coral bleaching this year follows closely after another global event that ended recently, creating accumulated stress for the organisms. A major scientific report published in August revealed that overall hard coral cover between 2020 and 2024 was lower than between 1980 and 2009, with record heat in 2024 causing the largest single-year drop so far. Researchers warn that temperatures will rise further as the El Nino reaches its full strength, raising risks for reefs worldwide.

Context

Coral reefs face recurring threats from global warming and El Nino cycles, which trigger widespread bleaching events by driving ocean temperatures too high. While scientists continue to test innovative restoration techniques like sound attraction and microbial treatments, experts stress that reducing greenhouse gas emissions remains essential for long-term survival.