Kategorie: News
Researchers warn of the consequences of increasing acidity on marine predators
Sharks are extremely successful predators in the ocean, whose excellent adaptation to their environment is largely due to their specialized teeth. These are perfectly suited for killing their prey. However, a recent study now warns that increasing ocean acidification could attack sharks' teeth and thus jeopardize their long-term survival.
A team led by zoologist Sebastian Fraune from Heinrich Heine University Düsseldorf has investigated the effects of acidification on shark teeth in the journal “Frontiers in Marine Science.” They found that acid-induced erosion of their teeth could have significant consequences.
The reason for the acidification lies in rising CO2 emissions, about a quarter of which is absorbed by the ocean. In water, CO2 reacts with water to form carbonic acid, which lowers the pH value. Shark teeth are particularly affected, as they consist largely of calcium phosphate - a mineral that is quickly damaged by acid attacks.
Like vinegar cleaner on limescale stains
“It's comparable to limescale stains in the bathroom, which you remove with vinegar cleaner,” explains study co-author Maximilian Baum. “It's the same with human teeth – the longer they are exposed to acid, the more the enamel suffers.” The crucial difference, however, is that sharks are in constant contact with seawater because their mouths are open to take in oxygen through their gills. This means that their teeth are permanently exposed to aggressive conditions.
To investigate the effects, the researchers collected teeth that had fallen out of blacktip reef sharks kept in captivity. After thorough cleaning, the teeth were immersed in artificial seawater with different pH values: one group in highly acidic water with a pH value of 7.3, the other in water with a pH value of 8.2 – the current average for the oceans. After eight weeks, the teeth were examined for changes in size, shape, and condition.
Damage to lost teeth
The results showed clear damage to the teeth kept in acidic water: they showed greater decomposition of the crown and root, with cracks and holes. In addition, the tooth volume changed, which can be attributed to the more aggressive effect of the acid. However, it is possible that the measurements were influenced by the rougher surfaces of the teeth.
Although the study was conducted under extreme conditions - the pH values correspond to projections for the year 2300 - the results point to possible real-world consequences for sharks. Decayed teeth could impair sharks' ability to break down prey, jeopardizing their survival. In addition, the altered tooth structure could increase the risk of breakage and disrupt the animals' calcium balance, which in turn increases their energy requirements.
“I wouldn't say that sharks will become extinct as a result of this development, but they are already under considerable pressure from overfishing, pollution, and ocean warming,” Baum summarizes. Acidification is another stress factor affecting the health of sharks.
It is unclear whether sharks can adapt to the changing environmental conditions. However, the study highlights how small changes in the ecosystem can have a major impact on animal species – with consequences for the entire food chain and the marine ecosystem.
Originalpublikation in „Frontiers in Marine Science“: www.frontiersin.org/.../fmars.2025.1597592/full
Prof. Dr. Sebastian Fraune: www.bmfz.hhu.de/.../prof-dr-ahmadian-reza