Sharks, those ancient predators that have roamed the oceans for hundreds of millions of years, are facing an unprecedented threat—and it’s not from fishermen, pollution, or even habitat loss. According to a study published in Frontiers in Marine Science and reported by TwistedSifter on October 16, 2025, the very teeth that have defined their dominance are eroding at a rate never before seen, thanks to the rapid acidification of our oceans.
It’s a story that might seem almost invisible to most people. After all, when we think of climate change, we picture melting glaciers, rising seas, or iconic land animals on the brink. But out of sight, beneath the waves, the chemistry of the ocean is shifting in ways that could spell disaster for entire marine ecosystems—starting with their most formidable hunters.
Ocean acidification, as explained in the recent research, is a direct result of our relentless burning of fossil fuels. The seas absorb excess carbon dioxide from the atmosphere, and this chemical shift is making the water more acidic. Scientists project that by the year 2300, ocean pH could be ten times more acidic than it is today—a staggering change for any living creature to endure.
To understand just how this acidification impacts sharks, researchers conducted a revealing experiment. They took undamaged shark teeth and placed them in tanks replicating two scenarios: one with a pH of 8.1, which matches current ocean conditions, and another at 7.3, the level scientists expect by 2300. The results were alarming. After only eight weeks in the more acidic water, the teeth developed cracks, holes, corrosion on their roots, and significant structural damage.
As biologist Maximilian Baum stated, "Shark teeth, despite being composed of highly mineralized phosphates, are still vulnerable to corrosion under future ocean acidification scenarios. They are highly developed weapons built for cutting flesh, not resisting ocean acid. Our results show just how vulnerable even nature’s sharpest weapons can be."
Sharks rely on their teeth not just for hunting, but for survival. If their teeth become brittle and prone to breaking, their ability to feed and, by extension, to reproduce and thrive, is compromised. While it’s true that sharks are famous for their ability to shed and regrow teeth—each individual can go through tens of thousands in a lifetime—the rate of damage observed in the study could easily outpace their natural regeneration cycles. Baum cautioned, "Even moderate drops in pH could affect more sensitive species with slow tooth replication cycles or have cumulative impacts over time. Maintaining ocean pH near the current average of 8.1 could be critical for the physical integrity of predators’ tools."
But what makes shark teeth so unique, and why are they so vulnerable? According to a National Geographic article published on October 17, 2025, sharks differ from most other vertebrates in a fundamental way: they have no bones. Instead, their skeletons are made entirely of cartilage—the same flexible, rubbery material found in human noses and ears. This cartilage is lighter and more flexible than bone, which allows sharks to swim with remarkable agility and speed.
This bonelessness is a defining trait of sharks and their relatives, the cartilaginous fishes—a group that includes rays, skates, sawfish, and chimaeras (ghost sharks). Their evolutionary lineage stretches back hundreds of millions of years, making them some of the oldest jawed vertebrates on Earth.
Shark teeth, however, are an exception to their otherwise cartilaginous bodies. They’re made of a hard inner core called dentin, covered by an even tougher outer layer known as enameloid. This unique structure is what gives their teeth their notorious bite—and also explains why fossilized shark teeth are often the only evidence paleontologists have of ancient species like the megalodon. Cartilage, unlike bone, doesn’t fossilize well, so those iconic teeth are often all that’s left behind.
But the very composition that makes shark teeth so formidable is also their Achilles’ heel in the face of acidifying oceans. The study’s findings suggest that even these highly mineralized structures are not immune to the corrosive effects of lower pH. If the trend continues, it’s not just individual sharks that are at risk—the ripple effects could destabilize entire marine food webs, since sharks play a crucial role as apex predators.
Why haven’t sharks evolved bones like so many other animals? The answer lies in their genetics. As National Geographic reported, a 2014 study by scientists at San Francisco State University found that sharks lack the genes required to convert cartilage into bone. Their genomes have remained largely unchanged for hundreds of millions of years, preserving their lightweight, flexible skeletons. This evolutionary path has served them well—until now.
Most sharks have between 200 and 400 cartilage structures supporting their bodies, a stark contrast to the 206 true bones found in adult humans. This lighter framework doesn’t just make them fast; it also compensates for the absence of a swim bladder, the gas-filled organ that helps bony fish control their buoyancy. Instead, sharks rely on a large, oil-filled liver to stay afloat.
Yet, it’s their teeth that have always been their most iconic feature. Sharks shed and regrow teeth continuously, leaving behind a trail of tens of thousands over their lifetimes. It’s not uncommon for beachcombers to stumble upon these prehistoric treasures washed up on the shore. In fact, scientists have used the size of fossilized teeth to estimate the size of extinct giants like megalodon—some of whose teeth are as large as a human hand.
Now, with ocean acidification accelerating, these very teeth are under threat. The implications stretch far beyond individual sharks. As their ability to hunt is compromised, so too is the delicate balance of marine ecosystems. Predators keep populations of other species in check, and any disruption at the top can cascade throughout the food web.
It’s a sobering reminder that the effects of climate change are often hidden from view, unfolding slowly but inexorably beneath the waves. The study’s authors warn that maintaining ocean pH close to its current average is critical—not just for sharks, but for the health of entire ecosystems that depend on them.
As the world grapples with the broader impacts of climate change, the plight of shark teeth serves as a sharp, if unexpected, wake-up call. Protecting the oceans from further acidification isn’t just about saving one species; it’s about preserving the intricate, ancient networks of life that have shaped our planet for eons.
