A new study reveals that increasing levels of carbon dioxide in the atmosphere, absorbed by the oceans, are making the water more acidic, posing a notable threat to marine life, including sharks. the research, which simulated future ocean conditions, found that shark teeth incubated in more acidic water experienced considerable damage to their roots and crowns, highlighting the far-reaching impacts of global climate change.

Sharks are renowned for their ability to constantly replace their teeth, a crucial adaptation for these apex predators as they rely on their teeth to capture prey. This continuous regeneration is vital for their survival.

However, scientists are concerned that even this remarkable ability may not be enough to protect sharks from the escalating pressures of ocean acidification. A team of German researchers discovered that more acidic ocean conditions lead to weaker and more brittle teeth.

“Shark teeth, despite being composed of highly mineralized phosphates, are still vulnerable to corrosion under future ocean acidification scenarios,” said first author of the frontiers in Marine Science article, maximilian Baum, a biologist at Heinrich Heine University Düsseldorf (HHU). “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.”

Damage from Root to Crown

Ocean acidification is an ongoing process characterized by a decrease in the ocean’s pH, resulting in more acidic conditions. This is primarily driven by the absorption of human-generated CO2 emissions. The current average pH of the world’s oceans is 8.1. Projections estimate that by 2300, it could drop to 7.3, making the ocean nearly ten times more acidic than it is today.

The research team utilized these pH values to investigate the effects of varying acidity levels on the teeth of Blacktip reef sharks. Divers collected over 600 discarded teeth from an aquarium housing these sharks. Sixteen undamaged teeth were selected for the pH experiment, while another 36 were used to measure circumference before and after the experiment. The teeth were incubated in separate 20-liter tanks for eight weeks. “This study began as a bachelor’s project and grew into a peer-reviewed publication. It’s a great example of the potential of student research,” said the study’s senior author, Prof Sebastian Fraune, who heads the zoology and Organismic Interactions Institute at HHU. “Curiosity and initiative can spark real scientific revelation.”

The results showed that teeth exposed to the more acidic water (pH 7.3) suffered significantly more damage compared to those incubated at the current average pH of 8.1. “We observed visible surface damage such as cracks and holes, increased root corrosion, and structural degradation,” said Fraune.tooth circumference also appeared greater at higher pH levels, not due to actual growth, but because the surface structure became more irregular, leading to a larger appearance in 2D images. While this altered surface might enhance cutting efficiency, it could also weaken the teeth structurally, making them more susceptible to breakage.

Small Damage, Big Effects

Notably the study focused solely on discarded teeth, which consist of non-living mineralized tissue. This means that any potential repair processes that might occur in living sharks were not taken into account. “In living sharks, the situation may be more complex. They could potentially remineralize or replace damaged teeth faster, but the energy costs of this would be probably higher in acidified waters,” Fraune explained.

Blacktip reef sharks, which must constantly swim with their mouths open to breathe, are particularly vulnerable, as their teeth are continuously exposed to the surrounding water. The researchers emphasized that if the water becomes too acidic, the teeth will inevitably suffer damage, especially as acidification intensifies. “Even moderate drops in pH could affect more sensitive species with slow tooth replication circles or have cumulative impacts over time,” Baum pointed out.”Maintaining ocean pH near the current average of 8.1 could be critical for the physical integrity of predators’ tools.”

Moreover, the study only examined the chemical effects of ocean acidification on non-living tissue. Future research should investigate changes to teeth in live sharks, focusing on their chemical structure and mechanical resilience. However,the current findings suggest that even microscopic damage could pose a significant threat to animals that rely on their teeth for survival.”It’s a reminder that climate change impacts cascade through entire food webs and ecosystems,” Baum concluded.

“Maintaining ocean pH near the current average of 8.1 could be critical for the physical integrity of predators’ tools.”