Story at a glance

  • Because of the vast amounts of carbon dioxide pumped into the atmosphere by human activities, the oceans are 30 percent more acidic than they were at the start of the industrial revolution.
  • The increasingly acidic ocean is having negative effects on marine life, especially creatures that form shells.
  • Researchers exposed sharks to seawater that simulated the acidity predicted for 2300 and found that it damaged the sharks’ skin. This could make the sharks more vulnerable to injury and disease while making them slower in the water by increasing drag.

Sharks have some of the toughest skin in the ocean. But as climate change makes seawater more acidic, even shark skin will start to suffer, according to new research.

Scientists exposed sharks to seawater that had been altered to mimic the conditions predicted for the year 2300, and found the caustic water corroded their armor-like skin, Science News reports. This damage to the shark’s denticles, the small, toothy structures that make up shark skin, could make them more vulnerable to infection or injury and slow them down by increasing drag.

The oceans are becoming more acidic because as humans have pumped more and more of the greenhouse gas carbon dioxide into the atmosphere, more and more has been absorbed by the oceans. Around 27 percent of all carbon dioxide emitted since 1959 has ended up dissolving into the oceans. 

When seawater mixes with carbon dioxide, it forms carbonic acid which makes the oceans more acidic. The oceans are now roughly 30 percent more acidic than they were before the start of the industrial revolution.

This has caused problems for creatures that make shells out of calcium carbonate, like clams and oysters, and has even been shown to impair fish hearing, vision and sense of smell

To test the potential impacts these increasingly acidic conditions might have on sharks, scientists exposed three puffadder shysharks to the corrosive seawater expected in 2300 for nine weeks. Using a scanning electron microscope to get an up-close look at the sharkskin, the researchers observed that 25 percent of the skin’s denticles were damaged by the corrosive waters — dulling the denticles’ pointed edges and their usually sleek surfaces. It takes longer than nine weeks to form new denticles, so the study did not establish whether exposure to acidic seawater impacts their development.

Other researchers were surprised by the results and are eager for similar tests on other species — particularly fast open-water species like the shortfin mako, which rely more heavily on speed to survive.

Published on Jan 06, 2020