Sharks have long been known for their razor-sharp teeth, weapons that make them some of the ocean’s most effective hunters. But new research suggests that these powerful tools may not be as invincible as once thought. German scientists have found that ocean acidification — the gradual drop in ocean pH caused by human-generated carbon dioxide — can weaken shark teeth, making them more prone to damage.

The study, published in Frontiers in Marine Science, examined the effects of simulated acidified seawater on teeth collected from blacktip reef sharks (Carcharhinus melanopterus). Researchers showed that even though shark teeth are highly mineralized and built to cut through flesh, they are still vulnerable to the corrosive effects of more acidic oceans. The findings raise questions about how sharks will fare in the future, when ocean chemistry is expected to be very different from today.

“Shark teeth, despite being composed of highly mineralized phosphates, are still vulnerable to corrosion under future ocean acidification scenarios,” said first author Maximilian Baum, a biologist at Heinrich Heine University Düsseldorf. “They are high developed weapons built for cutting flesh, not resisting ocean acid. Our results show just how vulnerable even nature’s sharpest weapons can be.”

To assess how acidification affects shark teeth, the team collected more than 600 naturally shed teeth from blacktip reef sharks housed at the Sealife Oberhausen aquarium in Germany. Sixteen of the best-preserved teeth were then incubated for eight weeks in seawater tanks set to two different pH levels: today’s average of 8.2 and the projected 2300 much more acidic level of 7.3. Another 36 teeth were used to measure before-and-after changes in size and surface condition.

The teeth placed in the more acidic water showed obvious signs of damage. Using scanning electron microscopes, the researchers detected cracks, holes and increased corrosion of the root structures. The crowns of the teeth responsible for gripping and slicing prey also showed visible wear. Even the serrated edges, critical for tearing through flesh, lost some of their fine detail. Teeth in the control group, held at today’s ocean pH, were in far better condition.

During the experiments, the team noted that the teeth in the more acidic 7.3 pH water appeared larger when measured in 2D images. This wasn’t actual growth but rather a result of surface irregularities caused by corrosion. While these rougher surfaces might seem like they could increase cutting efficiency, the researchers warned that they also make teeth structurally weaker and more likely to break.

For sharks, teeth are everything. Unlike humans, who have one set of baby teeth and one set of adult teeth, sharks continuously shed and replace theirs throughout life. A single shark might go through thousands of teeth. But if those teeth are weaker or more prone to breakage, it could reduce the efficiency of feeding. Sharks already face high energy demands and rely on their teeth to catch and process prey. Damage to these tools could mean they burn more energy while gaining less food.

The blacktip reef shark provides a good case study. This species must swim with its mouth open to breathe, exposing its teeth constantly to the surrounding water. That makes them especially vulnerable if the water grows more acidic.

“Even moderate drops in pH could affect more sensitive species with slow tooth replication circles or have cumulative impacts over time,” Baum said. “Maintaining ocean pH near the current average of 8.1 could be critical for the physical integrity of predators’ tools.”

It is important to note that this study only looked at discarded, non-living teeth. That means the results reflect purely chemical corrosion, without considering biological processes that might protect or repair teeth in live sharks.

So, for example, sharks could possibly remineralize damaged teeth or speed up tooth replacement when living under acidic conditions. But these processes likely require more energy, which could be another challenge in a changing ocean.

The study proves that even just microscopic damage might be enough to pose a serious problem for any animals that depend on their teeth for survival.

“It’s a reminder that climate change impacts cascade through entire food webs and ecosystems,” Baum said.