Even the fiercest predators in the sea aren’t immune to climate change—and their weakness may lie in a place no one expected.
Sharks have earned their fearsome reputation thanks to jaws lined with razor-sharp teeth that regenerate constantly. It’s this endless renewal that gives them an edge: without it, they’d be powerless to hunt. But in a rapidly changing ocean, even this clever survival trick might not be enough.
A team from Germany’s Heinrich Heine University in Düsseldorf (HHU) has been studying blacktip shark teeth in different acidification scenarios, and their findings—published in Frontiers in Marine Science—are sounding the alarm. The more acidic the water, the more the teeth begin to deteriorate.
“These are natural weapons made to tear through flesh—not to survive ocean acid,” said Maximilian Baum, a biologist at HHU and the study’s lead author.
A blacktip reef shark at Sealife Oberhausen, where the researchers collected the teeth for study. © Maximilian Baum
Hidden damage that’s easy to miss
Right now, the average pH of ocean water is around 8.1. But thanks to rising CO₂ emissions, that number could drop to 7.3 by the year 2300—making the ocean nearly ten times more acidic. To get a glimpse of this possible future, researchers gathered over 600 discarded shark teeth from an aquarium tank that housed blacktip sharks.
Sixteen intact teeth were selected for an eight-week trial in separate 20-liter tanks—some in normal pH 8.1 water, others in highly acidic pH 7.3. Another 36 teeth were measured before and after exposure.
The outcome was striking. Compared to those kept in neutral water, the teeth in acidic conditions developed cracks, holes, root erosion, and visible signs of structural decay. Even the shape changed. 2D imaging revealed that the teeth had wider circumferences—not from growth, but because the surface had become uneven and rough.
Assessment of tooth base damage. To assess the overall condition of the base, teeth were classified as (A) 1 = no damage, (B) 2 = minor damage, (C) 3 = moderate damage, (D) 4 = significant damage. © M. Baum et al. 2025
That uneven surface creates a strange double-edged sword. While a rougher texture might improve the tooth’s slicing ability, it also makes it weaker—more likely to crack and break.
A threat to survival
The study, which started as an undergraduate research project, ended up as a peer-reviewed publication. “It shows how valuable student-led research can be. Curiosity and initiative often lead to major insights,” noted Professor Sebastian Fraune, head of HHU’s Institute of Zoology and Organismic Interactions.
Importantly, the study was done using non-living, mineralized teeth that couldn’t repair themselves. In the wild, living sharks might be able to remineralize or grow new teeth—but in more acidic waters, that natural fix could take more energy than it’s worth. Future research will need to dive deeper into the chemical composition, physical changes, and resilience of living shark teeth.
The concern is especially urgent for species like blacktip sharks, which swim with their mouths open—leaving their teeth in constant contact with seawater. Even a slight dip in pH could cause gradual but damaging effects, particularly for species that don’t replace teeth as quickly. And even microscopic damage could be enough to interfere with their ability to hunt.
“Holding the ocean’s pH close to today’s average of 8.1 might be critical to keeping predator tools intact,” Baum warned. “It’s a powerful reminder that climate change has cascading effects across entire food webs and marine ecosystems.”
If the teeth of top predators are already showing signs of wear, what other essential features of marine life might start failing next? And more importantly—are we ready for what happens when these hidden cracks start spreading?
Cécile Breton
Journalist
Since childhood, books, photography, and travel have been part of my world. Fascinated by life, by the stars, by landscapes that tell stories without a single word, I quickly realized that I needed to express what I saw and felt.
Passionate about the world around me, I first pursued a degree in History at university, driven by my fascination with the stories of the past and the great civilizations that shaped our world. But over the years, another truth became clear: I didn’t want to spend my life in archives or research. I wanted to be out in the field, behind a camera or in front of a microphone, sharing what I learned.
So, I took a new path. I chose journalism, to learn how to tell stories differently—with rigor and clarity. I learned how to write, to interview, to edit, to capture both attention and emotion.
Giving meaning and sharing what matters
Since then, I’ve worked across different media: print, web, radio, television, and video. All of this has allowed me to bring to life topics that matter deeply to me: nature, animals, space, and the major environmental and human issues of our time.
Today, I continue my journey as a journalist at Futura. As part of the editorial team, I strive to share knowledge with curiosity, clarity, and passion. My guiding thread? To make visible what deserves to be seen, understood, and shared—and to keep my sense of wonder alive.
