Shark teeth can resist ocean acidification



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Shark teeth can resist ocean acidification

Due to the acidification of the oceans, marine fauna is in serious danger. The lowering of the marine pH creates the phenomenon of coral bleaching; the calcium carbonate that makes up shells, molluscs, crustaceans and even coral, decreases in relation to the increase in acidity, thus losing the algae that live above the surface of the organism, leading it to death.

Although many organisms suffer from this increasing acidification, some photosynthetic organisms benefit from it. One case is represented by diatoms; that is microscopic algae belonging to phytoplankton. For these organisms, the increase in CO2 in water increases their ability to carry out their own photosynthesis processes.

These processes can be carried out if in the presence of certain environmental conditions. Shark teeth can resist ocean acidification, research published on the Global change biology, makes an interesting retrospective on this topic: "Ocean acidification can cause dissolution of calcium carbonate minerals in biological structures of many marine organisms, which can be exacerbated by warming.

However, it is still unclear whether this also affects organisms that have body parts made of calcium phosphate minerals (e.g. shark teeth) , which may also be impacted by the 'corrosive' effect of acidified seawater.

Thus, we examined the effect of ocean acidification and warming on the mechanical properties of shark teeth, and assessed whether their mineralogical properties can be modified in response to predicted near-future seawater pH (-0.3 units) and temperature (+ 3 ° C) changes.

We found that warming resulted in the production of more brittle teeth (higher elastic modulus and lower mechanical resilience) that were more vulnerable to physical damage. Yet, when combined with ocean acidification, the durability of teeth increased so that they did not differ from those raised under ambient conditions.

The teeth were chiefly made of fluorapatite (Ca5 (PO4) 3 F), with increased fluoride content under ocean acidification that was associated with increased crystallinity. The increased precipitation of this highly insoluble mineral under ocean acidification suggests that the sharks could modulate and enhance biomineralization to produce teeth which are more resistant to corrosion.

This adaptive mineralogical adjustment could allow some shark species to maintain durability and functionality of their teeth, which underpins a fundamental component of predation and sustenance of the trophic dynamics of future oceans."