As global carbon dioxide emissions continue unabated, the world’s oceans are undergoing a profound chemical transformation with significant implications for marine life. A groundbreaking study led by a team of biologists at Heinrich Heine University Düsseldorf (HHU) has uncovered critical evidence that ocean acidification – a direct consequence of increased atmospheric CO₂ – threatens the structural integrity of shark teeth, potentially undermining one of nature’s most formidable predators. Published recently in Frontiers in Marine Science, this research elucidates the vulnerabilities of shark dentition when exposed to increasingly corrosive seawater conditions projected for the year 2300.
The phenomenon of ocean acidification stems from the ocean’s absorption of excess carbon dioxide emitted by anthropogenic activities. As CO₂ dissolves into seawater, it reacts to form carbonic acid, driving down the ocean’s pH and increasing acidity. This alteration in seawater chemistry jeopardizes calcareous structures across numerous marine organisms, but its impact on shark teeth – composed predominantly of highly mineralized phosphate compounds – has remained comparatively unexplored until now. The HHU team’s findings reveal that the microstructure of these teeth is far more fragile under acidified conditions than previously anticipated.
Sharks possess one of the most efficient biological tooth replacement systems in the animal kingdom, with teeth continuously developing and replacing those lost to wear and damage. This unique adaptation has historically guaranteed sharks’ evolutionary success as apex predators. However, the new research indicates that ocean acidification may compromise the very materials that make shark teeth robust weapons. By destabilizing the mineralized matrix of the teeth, acidified oceans could lead to increased rates of tooth fracture and wear, potentially impairing sharks’ feeding efficiency and survival.
To empirically assess the effects of acidification, researchers collaborated with Sealife Oberhausen, a marine aquarium that provided blacktip reef sharks (Carcharhinus melanopterus) teeth naturally shed in captivity. These teeth were subjected to two controlled seawater environments: one emulated current ocean pH levels averaging 8.1, while the other reflected projections for the year 2300, with pH artificially lowered to 7.3. The experimental setup simulated these conditions over an eight-week period, providing a rigorous comparative analysis of structural degradation.
Under microscopic examination at HHU’s Center for Advanced Imaging, the teeth incubated in water with reduced pH displayed stark morphological damage. Surface irregularities appeared in the form of microscopic cracks, holes, and widespread corrosion affecting both the roots and crowns of the teeth. This deterioration disrupts the surface uniformity and induces microstructural weaknesses, rendering the teeth significantly more prone to breaking under mechanical pressure. These findings represent the first direct evidence that ocean acidification impacts phosphate-rich dental tissues, highlighting a novel vulnerability previously unaccounted for in marine predator ecology.
Maximilian Baum, the lead author of the study and a former HHU student, emphasized the significance of these results, stating that while shark teeth are remarkably mineralized and designed for durability, they remain susceptible to chemical erosion by acidified seawater. He warned that this erosion could outpace the shark’s natural tooth replacement capabilities, introducing a potential bottleneck in their predatory efficiency. The consequences of such impairment could cascade through marine ecosystems, affecting food web dynamics and biodiversity.
Professor Dr. Sebastian Fraune, corresponding author and ichthyologist at HHU, reflected on the sophisticated functional design of shark teeth, noting their evolutionary optimization for cutting and tearing flesh. “Our investigation demonstrates that even the sharpest biological tools are fragile in the face of dramatic environmental change,” he explained. The study raises the possibility that beyond physiological limits of repair and regeneration, sharks may confront ecological pressures from diminished hunting proficiency.
Importantly, the study acknowledges inherent limitations, as it only examined naturally shed teeth outside living organisms. Aquarium curator and co-author Timo Haussecker highlighted that living sharks might possess some capacity for remineralizing and repairing damage to their teeth, though at potentially increased energetic costs. These physiological compensations could be overwhelmed by persistent and accelerated acidification, especially in species with slow tooth replacement cycles or those inhabiting more acidic niches.
From an ocean chemistry perspective, the pH reduction from 8.1 to 7.3 corresponds to an almost tenfold increase in hydrogen ion concentration, underscoring the severity of expected future acidification. This magnitude of change would not merely be a minor shift in water properties but represents a fundamentally altered chemical environment influencing mineral solubility and the stability of bioapatite – the mineral complex integral to shark teeth hardness.
The implications of these findings extend beyond shark biology, signaling a dire warning for marine ecosystems at large. Sharks serve as keystone predators, regulating prey populations and maintaining ecological balance. Any decline in their predatory effectiveness could precipitate trophic cascades with unforeseen repercussions throughout coral reefs, coastal habitats, and pelagic zones. This study amplifies the urgency for addressing carbon emissions and mitigating long-term chemical shifts in oceanic systems.
In conclusion, the HHU-led investigation into simulated ocean acidification’s effects on shark dental morphology uncovers a critical, previously underappreciated risk: the degradation of shark teeth integrity threatens their feeding mechanics and survival prospects. This novel research bridges marine chemistry and predator ecology, illustrating how anthropogenic change permeates biological design at the microscopic level. Safeguarding ocean pH stability emerges as a pivotal factor in conserving not only sharks but the intricate web of life reliant on their ecological roles.
Subject of Research: Impact of ocean acidification on shark tooth morphology and integrity
Article Title: Simulated ocean acidification affects shark tooth morphology
News Publication Date: 27-Aug-2025
Web References:
https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2025.1597592/full
References:
Baum M., Haussecker T., Walenciak O., Köhler S., Bridges C.R., Fraune S. Simulated ocean acidification affects shark tooth morphology. Frontiers in Marine Science 12: 1597592 (2025). DOI: 10.3389/fmars.2025.1597592
Image Credits:
Maximilian Baum (Blacktip reef shark at Sealife Oberhausen)
Keywords:
Ocean acidification, Marine fishes, Shark teeth, Tooth morphology, Ocean chemistry, Climate change, Marine ecosystems
