Scientists have detected a dramatic 40% drop in blue whale vocalisations in the Pacific, warning of ecosystem-wide impacts from record marine heatwaves. A new study in PLOS One links extreme ocean warming to collapsing food sources and toxic algae blooms, causing the largest marine mammal poisoning ever documented. Experts warn these changes are a sign of accelerating climate stress on oceans.
Researchers are alarmed after noticing a significant drop in the number of vocalizations from blue whales.
As National Geographic reports, scientists used specialized underwater hydrophones, meaning the aquatic version of microphones, to record and trace the sounds of marine life, allowing them to analyze the impact human activity is having on various species.
However, as detailed in a study published in the journal PLOS One, devastating heat waves have triggered worrying changes over the past decade, allowing toxic algae to bloom and undermine food sources for whales.
“It caused the most widespread poisoning of marine mammals ever documented,” coauthor and Monterey Bay Aquarium Research Institute biological oceanographer John Ryan told NatGeo. “These were hard times for whales.”
As a result, blue whale vocalizations dropped by almost 40 percent, according to the study, with populations of krill and anchovy collapsing.
“When you really break it down, it’s like trying to sing while you’re starving,” Ryan explained. “They were spending all their time just trying to find food.”
Scientists are still racing to understand the causes of devastating marine heatwaves. An ominous pool of warm water in the ocean, nicknamed “The Blob” following its discovery in early 2013, confounded scientists.
By 2016, it had grown to a region spanning over 2,000 miles in the Pacific Ocean, NatGeo reports.
The rising temperatures caused important sources of sustenance for blue whales to all but vanish.
Scientists are still racing to understand the effects of rising ocean temperatures. And as climate change continues to rear its ugly head, scientists are worried about future extreme weather events, including marine heatwaves.
Scientists have found that the duration of these heatwaves has tripled since the 1940s.
“There are whole ecosystem consequences of these marine heat waves,” coauthor and Monterey Bay Aquarium marine biologist Kelly Benoit-Bird told NatGeo. “If they can’t find food, and they can traverse the entire West Coast of North America, that is a really large-scale consequence.”
Worse yet, “fewer feeding opportunities” mean that blue whales “put less effort into reproduction,” as Oregon State University ecologist Dawn Barlow added.
“Where they are, and what they’re doing can tell you a lot about the health of the ecosystem,” Barlow explained. “The Blob really highlighted how long-term these consequences can be.”
Benoit-Bird voiced concerns of reaching a “tipping point,” which could have devastating consequences on our climate, changing how the “ocean absorbs carbon.”
“Science shows that climate change is impacting the oceans,” Barlow told NatGeo. “Listening and learning from these places is essential to our future. Now more than ever, it’s important to listen.”
Blue whales going silent
In a study published earlier this year, which traced more than six years of acoustic monitoring in the central California Current Ecosystem, Ryan and a team of researchers found clear patterns in whale song across seasons and years. By chance, the recordings began during a massive marine heatwave unlike anything seen before in the region.
As a result, blue whale vocalizations dropped by almost 40 percent, according to the study, with populations of krill and anchovy collapsing.
“When you really break it down, it’s like trying to sing while you’re starving,” Ryan explained. “They were spending all their time just trying to find food.”
The trouble started with a strange patch of unusually warm water in the Pacific Ocean, nicknamed “The Blob.” Discovered in 2013, it expanded by 2016 into a vast area spanning over 2,000 miles. The spike in ocean temperatures devastated essential food sources for whales.
Scientists are still racing to understand the causes of devastating marine heatwaves. An ominous pool of warm water in the ocean, nicknamed “The Blob” following its discovery in early 2013, confounded scientists.
Blue whales mysteriously going silent off California coast —alarming scientists https://t.co/ebsFvp3nYt pic.twitter.com/XI3q2DrCuG
— New York Post (@nypost) August 7, 2025
Are rising ocean temperatures affecting blue whales?
Scientists are still racing to understand the effects of rising ocean temperatures. And as climate change continues to rear its ugly head, scientists are worried about future extreme weather events, including marine heatwaves. Scientists have found that the duration of these heatwaves has tripled since the 1940s.
Kelly Benoit-Bird, a marine biologist at the Monterey Bay Aquarium, said, “There are whole ecosystem consequences of these marine heat waves. If they can’t find food, and they can traverse the entire West Coast of North America, that is a really large-scale consequence.”
Oregon State University ecologist Dawn Barlow added, “Fewer feeding opportunities” mean that blue whales “put less effort into reproduction.” Barlow emphasized that their movement and behavior reveal a lot about ocean health. “Where they are, and what they’re doing can tell you a lot about the health of the ecosystem.
Benoit-Bird voiced concerns of reaching a “tipping point,” which could have devastating consequences on our climate, changing how the “ocean absorbs carbon.”
“Science shows that climate change is impacting the oceans,” Barlow told NatGeo. “Listening and learning from these places is essential to our future. Now more than ever, it’s important to listen.”
Scientists Alarmed by Approaching Climate Tipping Point
The decline in whale vocalisations reflects deeper instability in marine environments. Benoit‑Bird cautioned that ecosystems may be approaching a tipping point, potentially altering how oceans absorb carbon, a critical factor in regulating Earth’s climate. “If these systems collapse, the consequences won’t stop at marine life,” she noted.
Barlow echoed the call for action, telling NatGeo: “Science shows that climate change is impacting the oceans. Listening and learning from these places is essential to our future. Now more than ever, it’s important to listen.” Researchers say continued monitoring using underwater acoustic tools will be key to understanding how marine life adapts to a rapidly warming ocean.
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