Acidified Oceans Found to Corrode Scales of South African Sharks

(CN) – Extended exposure to ocean water that has become too acidic as a result of global carbon dioxide emissions corrodes the scales of certain sharks, according to a new study published Thursday in Scientific Reports.

The puffadder shyshark. (By derekkeatsPuffadder shyshark, CC BY-SA 2.0, Link)

The study, led by Lutz Auerswald at the Stellenbosch University and a team of researchers, reveals that a certain type of shark species, puffadder shysharks, are at a risk of having some of their vital scales worn down by an ocean environment that has become far too acidic. While the consequences of an overly acidic ocean have been long discussed and examined among scientific circles, this study shows for the first time how damaging prolonged exposure can be on shark scales.

Researchers made this discovery by observing how three puffadder shysharks reacted to living in acidified for a total period of nine weeks. Researchers found that this kind of long-lasting exposure to the acidified water created a negative, corrosive reaction for some of the sharks’ scales.

Specifically, researchers found the most damage to the sharks’ denticles, teeth-like scales that cover the outer skin of puffadder shysharks. After the nine weeks in the acidified water, researchers discovered corrosion on up to a quarter of the denticles on the puffadder shysharks. For comparison, three other sharks in ocean water that was not overly acidic experienced only 9.2% denticle loss.

Scientists fear the findings indicate that as sharks suffer from a denticle loss as a consequence of an acidified ocean, their ability to swim and survive could be severely hindered. Researchers note denticles play a key role in how sharks navigate, and should they corrode, a shark could find itself with a decreased swim speed a less protected scale layer.

The study also suggests it is possible that acidified ocean water could have a corrosive effect on a shark’s teeth. Considering that the chemical makeup and structure of a sharks’ denticles are the same as a shark’s teeth, it is fair to assume both parts of a shark could be corroded in acidifying oceans.

“Denticle corrosion and the resultant increase in denticle turnover can potentially compromise hydrodynamics and skin protection. As denticles and shark teeth are structurally and materially identical, chemical dissolution of teeth at a similar rate can be expected,” according to the study.

Researchers say that with a shark’s teeth being its primary tool for hunting and feeding, a shark with corroded teeth would find itself significantly jeopardized and placed at an extreme risk in the wilds of the ocean.

Auerswald said these results are completely unpreceded and came as a shock to researchers.

“Of all results from our research paper, the corrosion of the denticles came as a surprise. We did not expect this. We know from human dentistry that teeth (also dentin) get damaged by carbonated drinks. However, they are much more acidic than the pH of 7.3 we used in our study,” Auerswald said in an email. “Also, there was no previous evidence that showed that dentin is affected by acidified seawater.”

The study reports, however, that hope is not lost for puffadder shysharks. Researchers found that despite being in an acidic environment, sharks adapted to their surroundings in one key way: their blood. As the sharks spent more times in acidified water, scientists found that concentrations of carbonate increased in their bloodstreams. This is turn allowed the shark’s blood from becoming overly infused with acidic chemicals like carbon dioxide.

Researchers hope their findings could point to a shark’s ability to adapt to changing climate conditions and find effective ways to endure new environments.

Despite this potential positive, the study warns that increased acidified oceans still pose significant dangers to these shark communities, especially those that are confined to certain sections of the ocean like the ones studied in Africa.

“We speculate that a combination of these multiple effects might negatively affect the populations of this and other endemic, coastal elasmobranch species for which range shift is impossible as they reside at the southern tip of the African continent,” the study states.

The study concludes by emphasizing the imperative nature of continued testing on this issue to determine the true scope of the problem itself and to truly understand the consequences of Earth’s increasingly acidic oceans.

%d bloggers like this: