Sharks’ teeth are corroding due to acidic waters: study

They’re more shark than bite.

Sharks could soon experience a dental breakdown. These apex predators are at risk of losing their teeth due to the increased acid content in the world’s oceans, according to a literal Jaws-dropping study published in the journal Frontiers in Marine Science.

“Shark teeth, despite being composed of highly mineralized phosphates, are still vulnerable to corrosion under future ocean acidification scenarios,” said the study’s lead author Maximilian Baum, a biologist at Heinrich Heine University Düsseldorf (HHU), per Science Daily.

The study comes as the world’s oceans have become 30% more acidic than before the Industrial Revolution, which experts attribute to a spike in carbon dioxide emitted by cars, factories, and power stations, the Times of London reported.

This spike in acidity is wreaking havoc on sea urchins, coral reefs and other organisms that rely on calcium bicarbonate in the sea to construct their shells. A 2020 study found that warming temperatures and increased acidification could wipe out all coral reefs by 2100.

Baum and co were interested to discover how oceanic acidification is impacting shark teeth, which are built for slicing and dicing flesh.

To discover whether acidity was causing sharks’ gnashers to lose their edge, the German scientists gathered around 600 teeth shed by blacktip reef sharks at an aquarium.

They then placed them in two different tanks of water: One had a pH of 8.1 — equivalent to current ocean and the other with a pH of 7.3, the level forecast for the year 2300 should carbon emissions continue at the same rate.

They marinated the sea bass slicers in there for eight weeks before taking them out and comparing the results of the acid test.

Using an index to determine corrosion by area, the team found that the teeth in the more acidic tank had deteriorated around 50% more than the ones in other tank.

“We observed visible surface damage such as cracks and holes, increased root corrosion, and structural degradation,” said the study’s senior author, Prof Sebastian Fraune, who heads the Zoology and Organismic Interactions Institute at HHU.

While the more acidified teeth appeared bigger in the 2D images, they were structurally more brittle and therefore more prone to breaking.

From this, the team deduced that sharks’ dental hardware, formidable though it may be, is no match for the marine acidification scourge.

“They are highly developed weapons built for cutting flesh, not resisting ocean acid,” said Baum. “Our results show just how vulnerable even nature’s sharpest weapons can be.”

This molar meltdown is especially problematic for species like the blacktip reef shark, which must swim with their mouths permanently open to breathe, constantly exposing their chompers to this acid bath.

“Even moderate drops in pH could affect more sensitive species with slow tooth replication circles or have cumulative impacts over time,” observed Baum. “Maintaining ocean pH near the current average of 8.1 could be critical for the physical integrity of predators’ tools.”

The one caveat is that the team used the discarded teeth of non-living mineralized tissue and didn’t factor in the healing process or the fact that sharks’ teeth are constantly replaced by a conveyor belt of new chompers.

“In living sharks, the situation may be more complex,” said Fraune. “They could potentially remineralize or replace damaged teeth faster, but the energy costs of this would be probably higher in acidified waters.”

Ultimately, the researchers concluded that “acidification is not only impacting some small and tiny shelled [creatures] or corals, we also have effects for large marine predators,” said Baum.