Sharks are known for being able to replace their teeth, with new ones growing to replace older ones when they wear down. This is crucial for their survival as they rely on their teeth to catch their prey. 

A research team headed by Professor Dr Sebastian Fraune from the Institute of Zoology and Organismic Interactions at MUHS has, in collaboration with biologists from the Sealife Oberhausen marine aquarium, examined the impact of ocean acidification on shark teeth. They placed shark teeth in containers of water at different levels of acidity: at the current pH of the oceans and at the expected pH in 2300. 

“Shark teeth comprise highly mineralised phosphates, but they are susceptible to corrosion. The more acidic water in the simulated 2300 scenario damaged the shark teeth, including roots and crowns, much more than the water at the current acidity level. Global changes are thus so far-reaching that they can impact the microstructure of shark teeth,” says Maximilian Baum, former MUHS student and now a freelance diver, photographer and speaker. He is the lead author of the study. 

Corresponding author Professor Fraune: “The teeth are highly sophisticated weapons designed to cut flesh, but not to withstand the acidification of the oceans. Our results show how fragile even nature’s sharpest weapons can be. It is possible that the ability of sharks to replace their teeth on an ongoing basis will not be able to keep up with the changes in their environment.” 

Teeth shed naturally by blacktip reef sharks (Carcharhinus melanopterus) kept at Sealife Oberhausen were used for the study. These teeth were divided between separate containers – one holding seawater with a pH of 8.1 (the current level) and the other with a pH of 7.3 (what is expected in 2300) – and incubated for eight weeks. Baum: “This pH corresponds to an almost tenfold increase in acidity compared with today.”

The teeth were then examined under the microscope at the Center for Advanced Imaging at MUHS. Fraune: “At a pH-value of 7.3, we observed surface damage such as cracks and holes, increased root corrosion and structural deterioration. In addition, the surface morphology was more irregular, which can weaken the structure of the teeth and make them more susceptible to breaking.”

Timo Haussecker, Aquarium Curator at Sealife Oberhausen and co-author of the study: “As we only examined naturally shed teeth, the study does not take account of any repair processes, which may occur in living organisms. The situation may therefore be more complex in living sharks as they may be able to remineralise damaged teeth, albeit with greater energy expenditure.” 

“Even moderate decreases in pH-values can impact more sensitive species with slow tooth replacement cycles or have a cumulative effect over the course of time,” adds Baum. “For sharks, it is certainly of great importance that the pH-value of the oceans remains near the current average of 8.1.”

Maximilian Baum and Professor Fraune conclude: “Our research reminds us that anthropogenic changes can impact entire food webs and ecosystems.”

Original publication

Baum M., Haussecker T., Walenciak O., Köhler S., Bridges CR. and Fraune S.. Simulated ocean acidification affects shark tooth morphology. Front. Mar. Sci. 12: 1597592 (2025). 

DOI: 10.3389/fmars.2025.1597592

Aims of the series:

• To better understand social dynamics and mechanisms of discrimination.
• To recognise discriminatory behaviour and develop alternatives.
• To strengthen tolerance of ambiguity – dealing constructively with contradictions and uncertainties.
• To develop an attitude of solidarity and live it in everyday life.

Dates: 31 October, 7 November, 14 November and 21 November 2025, from 10 a.m. to 12 p.m. each day.

Registration at diversity(at)university.marienhospital-clinic.de.

This series of events offers a safe learning space for anyone who wants to sharpen their attitude and expand their options for action in the spirit of a discrimination-critical university.

The Occupational and Environmental Safety Unit (SAUS), the Heine-Center for Sustainable Development (HCSD) and Facility Management (Division 6) have put together further tips, e.g. on what to eat and the best temperature for your drinks.

The ten tips can be found in this PDF
 

You can also look forward to various activities throughout the campus, which we would like to invite you to take part in. The pantomime group MIME Art for Life e.V. will provide a creative supporting programme, which will creatively focus on the topic of diversity and give it visual expression.

The Diversity Award ceremony will take place from 14:15. This recognises university members from various status groups who have made an outstanding commitment to promoting diversity at the university. An independent committee of university representatives has selected and honoured one award winner each from the categories of teaching staff, employees and students from a large number of nominations received. We look forward to celebrating the award ceremony with you.