Study warns ocean chemistry changes could weaken sharks' teeth

Sharks are known as the ocean's most feared predators, relying on their razor-sharp, constantly regrowing teeth to survive. But scientists say rising ocean acidity could gradually weaken those powerful weapons.

That is the conclusion of a study by German researchers who examined how more acidic seawater affects shark teeth. Scientists say human activities such as burning coal, oil, and gas are increasing the amount of carbon dioxide absorbed by the oceans, making seawater more acidic.

The study found that as acidity increases, shark teeth could become structurally weaker and more prone to cracking and breaking. This could eventually threaten sharks' position at the top of the marine food chain.

"The ocean won't suddenly be filled with toothless sharks," said lead researcher Maximilian Baum, a marine biologist at Heinrich Heine University Düsseldorf. "But weaker teeth would be another serious threat for animals already facing pollution, overfishing, climate change, and habitat loss."

Baum said the team discovered clear signs of corrosion on shark teeth, warning that the predators' ecological dominance could be at risk over time.

The findings were published in the journal Frontiers in Marine Science as concern grows worldwide over ocean acidification. According to the US National Oceanic and Atmospheric Administration (NOAA), acidification occurs when oceans absorb more carbon dioxide from the atmosphere. Scientists estimate the ocean could become nearly 10 times more acidic by the year 2300.

For the study, researchers collected more than 600 discarded teeth from an aquarium housing blacktip reef sharks, a species found in the Pacific and Indian oceans. The teeth were placed in water reflecting today's acidity levels and the projected acidity of the year 2300.

Teeth exposed to the more acidic water showed severe damage, including cracks, holes, root corrosion, and overall structural degradation.

The researchers said the results indicate ocean acidification will have a significant impact on the physical strength of shark teeth.

Shark teeth are highly specialised tools designed for slicing through flesh rather than resisting chemical corrosion. Over a lifetime, a shark can grow and lose thousands of teeth, which are essential for hunting and maintaining balance in marine ecosystems.

Many shark species are already under threat. According to the International Union for Conservation of Nature, more than a third of all shark species face the risk of extinction.

Nick Whitney, a senior scientist at the New England Aquarium who was not involved in the research, said the study was scientifically sound. However, he noted that shark teeth develop inside mouth tissue and may be somewhat protected from changing ocean chemistry for a time.

"Sharks have survived for about 400 million years and have adapted to many environmental changes," Whitney said.

Gavin Naylor, director of the Florida Program for Shark Research, said ocean acidification is a concern but stressed that overfishing remains the biggest threat to sharks worldwide.

Scientists also warn that acidification will affect much more than sharks. Shellfish such as oysters and clams may struggle to build shells, while fish scales could become weaker and more brittle.

Baum said ocean acidification should not be ignored as a growing danger for sharks. Some species are already close to extinction, and worsening ocean chemistry could push them even closer.

"The evolutionary success of sharks depends on their perfectly developed teeth," he said.