Scientists have observed that some of the fiercest hunters in the oceans are losing their bite. This is a consequence of oceans becoming more acidic, due to climate change; here, sharks’ teeth are becoming structurally weaker and more prone to breaking.
Scientists have found that future acidic waters will cause shark teeth to corrode, crack, and weaken. Consequently, this threatens their effectiveness as hunting weapons and will disrupt the food chain of the oceans. This observation highlights the hidden dangers impacting the ocean ecosystems.
Acidification of the seas
Ocean acidification refers to the long-term, global decrease in seawater pH caused primarily by the ocean’s uptake of carbon dioxide from the atmosphere. As carbon dioxide dissolves into seawater; this alters the carbonate chemistry that many marine organisms rely on to build shells and skeletons.
Sharks
“Shark teeth, despite being composed of highly mineralised phosphates, are still vulnerable to corrosion under future ocean acidification scenarios,” says first author of the Frontiers in Marine Science article, Maximilian Baum.
The ability of sharks to regrow teeth may not be enough to ensure they can withstand the pressures of a warming world. This is a state where oceans are getting more acidic. Scientists from Germany have examined sharks’ teeth under different ocean acidification scenarios and showed that more acidic oceans lead to more brittle and weaker teeth.
Research finding
The study only looked at discarded teeth of non-living mineralized tissue, which means repair processes that may happen in living organisms could not be considered.
The researchers used these two pH values to examine the effects of more and less acidic water on the teeth of Blacktip reef sharks. Divers collected more than 600 discarded teeth from an aquarium housing the sharks. The 16 teeth – those that were completely intact and undamaged – were used for the pH experiment, while 36 more teeth were used to measure the before and after circumference.
The shark teeth were incubated for eight weeks in separate 20-liter tanks. Compared to the teeth incubated at 8.1 pH, the teeth exposed to more acidic water were significantly more damaged.
The scientists observed visible surface damage such as cracks and holes, increased root corrosion, and structural degradation. For example, tooth circumference was also greater at higher pH levels. Teeth, however, did not actually grow, but the surface structure became more irregular, resulting in it appearing larger on 2D images. While an altered tooth surface may improve cutting efficiency, it potentially also makes teeth structurally weaker and more prone to breaking.
Next steps
Future studies are set to examine changes to teeth, their chemical structure, and mechanical resilience in live sharks. The current study shows that microscopic damage might be enough to pose a serious problem for animals depending on their teeth for survival.
Research paper
The study appears in the journal Frontiers in Marine Science, titled “Simulated ocean acidification affects shark tooth morphology.”
