Sharks are famous for their teeth. Unlike humans, they never run out—when one tooth falls out or wears down, another quickly takes its place.
This constant renewal has helped them remain some of the ocean’s most efficient predators for hundreds of millions of years.
But new research suggests that this remarkable adaptation might not be enough to protect them in a rapidly changing ocean.
A study by German researchers has found that ocean acidification—the gradual decrease in ocean pH caused by rising levels of carbon dioxide in the atmosphere—could be weakening shark teeth.
The results show that even these highly specialized tools, built for tearing through flesh, are vulnerable to corrosion in more acidic waters.
“Shark teeth, despite being made of strongly mineralized phosphates, are still at risk under future ocean acidification scenarios,” explained Maximilian Baum, a biologist at Heinrich Heine University Düsseldorf (HHU) and lead author of the study, which was published in Frontiers in Marine Science.
“They’re highly developed weapons designed for hunting, not for resisting acid. Our findings reveal just how vulnerable even nature’s sharpest weapons can be.”
Currently, the ocean’s average pH is around 8.1. But if carbon emissions continue at their present rate, that number could fall to 7.3 by the year 2300. While this difference might seem small, it would make oceans nearly ten times more acidic than they are today.
To test the effects, the team collected more than 600 discarded teeth from Blacktip reef sharks housed in an aquarium in Oberhausen, Germany.
Sixteen of the most intact teeth were chosen for an eight-week incubation experiment. Some were placed in tanks with normal seawater conditions (pH 8.1), while others were placed in water that was more acidic (pH 7.3).
The results were clear.
Teeth exposed to acidic water showed obvious signs of damage, including cracks, holes, and increased corrosion at the roots. The surface structures also became more irregular, making the teeth look slightly larger in two-dimensional images, though they were actually weaker.
While a rougher surface might theoretically help with cutting, the scientists noted that the structural damage would likely make teeth more fragile and more prone to breaking.
Professor Sebastian Fraune, senior author of the study and head of the Zoology and Organismic Interactions Institute at HHU, noted that the project began as a student research project before growing into a peer-reviewed paper. “Curiosity and initiative can spark real scientific discovery,” he said.
Importantly, the researchers stressed that the study only looked at discarded, non-living teeth. Living sharks might respond differently.
It is possible they could repair damaged teeth or replace them more quickly, but doing so would likely require more energy—an extra burden in a harsher environment. Since Blacktip reef sharks must swim with their mouths open to breathe, their teeth are constantly exposed to seawater, leaving them especially vulnerable if the oceans become more acidic.
Even small drops in pH could cause problems for shark species that regenerate teeth more slowly, or for those that rely on long-term dental durability. Over time, microscopic damage could build up and threaten their ability to catch prey.
“Keeping ocean pH close to current levels may be critical for the survival of sharks and other predators that depend on their teeth,” Baum said.
He added that the study highlights how climate change and ocean acidification ripple through entire ecosystems, creating risks not just for sharks but for the food webs they dominate.
What may begin as tiny cracks in shark teeth could, in time, shake the foundations of life in the ocean.
