A mysterious mass die-off of whales millions of years ago may finally have an explanation – and it all starts with volcanoes.
Scientists suggest in a new study published in Natural communications that powerful eruptions in the Andes helped trigger toxic algae blooms. These blooms likely killed dozens of marine animals, whose fossilized remains were later discovered in Chile’s Atacama Desert. Additionally, this same chain reaction may also have helped cool the planet and set the stage for unprecedented ocean evolution.
The findings connect volcanism, ocean chemistry, marine ecosystems and climate in ways that researchers have not yet fully understood, revealing how a natural process can have a ripple effect on Earth’s systems.
Two of the researchers examine whale fossils at a site in Chile’s Atacama Desert.
(Image credit: Barbara Carrapa)
Ancient whale graveyard linked to Andean volcanoes and algae blooms
The story begins in 2010, when construction crews working along Chile’s Pan-American Highway discovered an extraordinary fossil site. Known as Cerro Ballena, or “Hill of the Whales,” it is home to more than 40 remarkably preserved marine animals, including whales and porpoises, dating back approximately 6 to 9 million years.
Once paleontologists examined the site, what intrigued them was not only how many fossils were there, but also how they died.
The animals appear to have died quickly and in the same location, suggesting a sudden, catastrophic event. Scientists suspected toxic algae blooms, but the trigger for the blooms remained unclear.
Around the same time, during the late Miocene, Earth experienced major environmental changes. The oceans were cooling and the whales themselves were evolving, with some species becoming considerably larger.
Researchers began looking to see if there was a unifying cause between ocean cooling and the mass death of whales.
Learn more: Toxic algae in whale droppings warns of warming seas in Alaska’s Arctic
How volcanic ash transformed the ocean
The missing piece of the puzzle was found in the Andes. During this period, intense volcanic activity accompanied the uprising of the famous mountain range. These eruptions released huge amounts of ash into the atmosphere, which eventually settled in the ocean.
These ashes contained essential nutrients like iron, phosphorus and silicon, elements that act as fertilizer for microscopic marine organisms.
“Once you put a lot of very important nutrients from volcanoes into the ocean, your primary producers will go crazy, because all of a sudden they will have a lot of nutrients available to them, and that, in turn, is going to affect the entire marine ecosystem,” first author Barbara Carrapa said in a press release.
In some areas, this surge likely supported larger marine animals, including whales. But in other areas, like Cerro Ballena, it has had darker consequences. Some algal blooms produced toxins that accumulated in the food chain, ultimately poisoning large marine mammals.
Climate change hidden in the ocean
The implications of what the research team discovered go far beyond the deaths of ancient whales.
As phytoplankton populations grew, they also took up large amounts of carbon dioxide through photosynthesis. When these organisms died, much of this carbon sank to the bottom of the oceans, removing it from the atmosphere.
This process, known as carbon sequestration, may have contributed to global cooling at the end of the Miocene.
“Once we take into account the biological effects of volcanoes fertilizing the ocean, we can see a nice correlation between Andean volcanism and all the changes happening in the ocean,” Carrapa explained. “All of this together created the perfect storm where, if you put the ashes in the right place and ignite primary production, you end up affecting marine ecosystems as a whole, including whales.”
Overall, the study highlights a lesser-known side of volcanism. Although eruptions are often associated with the release of carbon dioxide and global warming, this research shows that they can also cause indirect cooling through ocean life.
“This work improves our understanding of how natural processes can regulate Earth’s climate, which is directly relevant to anticipating future climate change and its impacts on society,” concluded co-author Mark Clementz.
Learn more: Hidden underwater volcanoes could explain half of Earth’s Triassic extinctions
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