The Surprising Fragility of Shark Teeth

Explore

SHark’s teeth are a marvel of evolution. They are so sharp that many island cultures used to use them as weapons and tools to hunt and cut meat. Unlike the human teeth, the shark teeth line the mouth of these ocean predators by the dozen, up to 50 rows deep. Shark babies are born with complete sets so that they can start hunting from an early age. But these claws may not be up to the acidity of the ocean: as climate change gives a kick to the sea pH, some shark teeth collapse.

It is according to new research published this week in Borders in marine science. The ocean absorbs around 30% of carbon carbon emissions, which triggers a chemical reaction – when carbon dioxide dissolves in sea water, it becomes carbonic acid which leaves more hydrogen ions in the sea, lowering pH.

“Sharks are already faced with overfishing, pollution and warming seas,” explains Maximilian Baum, biologist at Heinrich Heine Düsseldorf University and the main study. “If acidification also compromises their teeth, this could reduce their feeding success and their overall resilience.”

Since the beginning of the industrial revolution in the middle of the 18th century, the average acidity of sea water has jumped by 30%, with a particularly dramatic change between the 80s and now. Some experts predict that the acidity of the ocean will double or triple in 2100, unless we considerably reduce carbon emissions.

Ruin teeth are just a way that climate change spoils with sharks.

This means a nightmare for the life of the sea, including sharks. Baum began to wonder if the increase in oceanic acidity could harm the shark teeth after reading a 2019 study demonstrating how their skin denticles are affected. “This led me to ask me if oral teeth, especially in constant exposure species of sea water, could show a similar vulnerability, because shark teeth are a homologous structure with skin denticles,” he said.

For the study, Baum naturally collected teeth from black reef sharks hosted with aquarium and incubated these samples in sea water with different levels of pH. He and the research team then analyzed the structural changes using imaging and morphological measures. The teeth exposed to more acidic water were clearly more damaged, demonstrating cracks and holes, increased corrosion of roots and structural degradation. These results could also apply to other species, which has an impact on sharks such as hammers, tigersharks and bullshit that swimming with wide open mouth, a form of passive breathing, adds Baum.

Ruin teeth are only a way that climate change spoils with sharks, making their house less hospital. The warming of oceans makes more difficult for shark eggs and juveniles to survive, increase the metabolism of sharks – which makes it more energy to swim and disturb their migratory schemes and the ecosystems on which they count. More extreme seasonal variations in the weather and storms also complicate the shark migration models and the ability to raise their young people. It does not matter that the fishing pressure has already resulted in a decrease of 71% of populations of sharks and ocean rays since the 1970s.

The main limitation of the study of the team is that it did not directly look at living sharks – which can be able to remineralize and replace the damaged teeth to avoid the worst impact, but there is the risk that the energy cost of this will be high, said Sebastian Fraune, study author and zoology teacher at Heinrich Heine Düsseldorf, in a press release.

Having fewer sharks around is a huge problem for the ocean – like APEX predators, they help regulate the populations of other creatures in their ecosystems. In an example, a decrease in sharks in the Caribbean led to the overcrowding of Méber, which then sparked a drop in people -fishing populations who are responsible for grazing algae from coral reefs – leaving too many algae which now recommend certain reefs. Another study demonstrated how the loss of sharks off the coast of the North Carolina took place in cascade in a complete fishing of scallops. Without forgetting, like whales, sharks act like massive carbon wells when they die and fall to the bottom of the ocean.

“Even the main very advanced predators are not immune to the changes of the ocean caused by humans,” explains Baum. “If their teeth are in danger, it shows how much environmental stress can reach deep in marine ecosystems. It influences almost everything, from the smallest shell to the largest predator. ”

Image of lead: Giovanni Nitti / Shutterstock

• Sara Kiley Watson

  Published on September 11, 2025

  Sara Kiley Watson is a climate and scientific journalist currently based in the Netherlands.