A recent study from Heinrich Heine University in Düsseldorf, published in *Frontiers in Marine Science*, showed that ocean acidification, a consequence of increased carbon dioxide (CO₂), erodes shark teeth and compromises their hunting ability. Under simulated high-acidity conditions expected in 2300 (pH 7.3), blacktip shark teeth suffered twice as much damage in eight weeks, with cracking and corrosion at the base ([The Guardian](https://www.theguardian.com/environment/2025/aug/27/ocean-acidification-erodes-sharks-teeth-affecting-feeding?utm_source=chatgpt.com)).
The team was led by Maximilian Baum, a researcher at Heinrich Heine University Düsseldorf, along with marine chemists ([The Times](https://www.thetimes.co.uk/article/ocean-acidification-corrodes-shark-teeth-fk985lnw7?utm_source=chatgpt.com)). The experiments were carried out in Germany using naturally shed teeth from blacktip reef sharks, published August 27-28, 2025 ([Oceanographic Magazine](https://oceanographicmagazine.com/news/all-shark-no-bite-ocean-acidification-might-leave-species-toothless/?utm_source=chatgpt.com)).
Although the phenomenon is current, it has occurred millennia and millions of years ago. During the **Paleocene-Eocene Thermal Maximum** (~55.8 million years ago), a rapid increase in CO₂ caused global warming and ocean acidification, affecting calcifying organisms ([Paleo Nerdish](https://paleonerdish.wordpress.com/2017/10/24/brief-history-of-the-ocean-acidification-through-time-an-update/?utm_source=chatgpt.com)). In the **Permian Extinction** (~252 million years ago), the massive release of CO₂ reduced the pH by up to 0.7 units, eliminating numerous marine species ([Wikipedia – Permian Extinction](https://en.wikipedia.org/wiki/Permian%E2%80%93Triassic_extinction_event?utm_source=chatgpt.com)).
Other events included the **Toarcian OAE** in the Jurassic (~183 Mya), which acidified the oceans and generated anoxic zones ([Wikipedia – Toarcian OAE](https://en.wikipedia.org/wiki/Toarcian_Oceanic_Anoxic_Event?utm_source=chatgpt.com)), and the **Cenomanian–Turonian** in the Middle Cretaceous, where acidification coincided with extinctions of ammonites and corals ([Wikipedia – Cenomanian–Turonian](https://en.wikipedia.org/wiki/Cenomanian-Turonian_boundary_event?utm_source=chatgpt.com)). These examples show that acidification is not unprecedented, but the current rate is unprecedented in at least 300 million years ([Wired](https://www.wired.com/2012/03/ocean-acidification-peak?utm_source=chatgpt.com)).
Today, CO₂ concentrations have risen rapidly due to the burning of fossil fuels. Between 1950 and 2020, ocean pH decreased and acidity increased by 26%, much faster than in past geological events ([Wikipedia – Ocean Acidification](https://en.wikipedia.org/wiki/Ocean_acidification?utm_source=chatgpt.com), [EPA](https://www.epa.gov/ocean-acidification/understanding-science-ocean-and-coastal-acidification?utm_source=chatgpt.com)).
The consequences include a reduction in sharks' hunting ability if their teeth weaken, disruptions to corals, mollusks, and other calcifying organisms, and the risk of marine ecosystem collapse. The combination of acidification, global warming, and anoxia in the past warns that the planet could be entering a high-risk scenario for ocean biodiversity ([Ocean.si.edu](https://ocean.si.edu/ocean-life/invertebrates/ocean-acidification?utm_source=chatgpt.com), [AOL](https://www.aol.com/climate-change-threatening-nature-sharpest-040000281.html?utm_source=chatgpt.com), [Yale](https://people.earth.yale.edu/sites/default/files/files/Thomas/Hoenischetal-2012.pdf?utm_source=chatgpt.com), [EOS](https://eos.org/research-spotlights/exploring-ancient-ocean-acidification-in-the-rock-record?utm_source=chatgpt.com)).