Tuesday, December 24, 2019

Ocean Acidification Could Eat Away at Sharks’ Teeth and Scales


By Rachel Nuwer on December 19, 2019

Sharks are some of the world’s most formidable predators, but their place at the top of the marine food chain may be threatened by ocean warming and acidification. As carbon dioxide levels in the oceans increase, upping the acidity of the water, shark teeth and scales may begin to corrode, compromising their ability to swim, hunt and feed, according to research published today in Scientific Reports.

Ultimately, sharks could be displaced as apex predators, disrupting entire ocean food webs, says the study’s senior author Lutz Auerswald, a fisheries biologist at Stellenbosch University in South Africa and the nation’s Department of Agriculture, Forestry and Fisheries. “Some of the bigger species, like great white sharks, are also already highly endangered, so this might wipe them out.”


The impacts, however, would likely vary between species, Auerswald says. Puff adder shy sharks are sedentary predators that ambush their prey, so corroded scales might not impact their ability to hunt. But for larger species that swim in open water, such as great white sharks, scales play an important role in hydrodynamics. One study found that shark denticles are responsible for an up to 12 percent increase in swimming speed. Thus, damaged denticles could slow sharks down and make it more difficult for them to catch prey. Scales also protect females from male biting during courtship and help some shark species defend against other predators. Likewise corrosion to teeth could hit some species harder than others.


“A lot of animals have survived even more acidic conditions in the ancient past, but we also know that a lot of species were wiped out,” Auerswald says. “One lesson is that you have to test species by species.”

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