Even if these elements don’t kill the sharks, Wosnick and Bond worry about the sublethal effects. The rare earths, particularly titanium, could cause oxidative stress in the liver, Wosnick says. The energy the sharks expend to deal with this stress could affect their ability to hunt prey or reproduce.
Scientists know a little more about titanium than the other elements, Bond says. Titanium can have “really damaging effects” on the kidneys and the barrier that allows oxygen to pass from the blood to the brain. If oxygen has trouble getting to the brain, it can cause a number of problems, including disorientation, which can also affect hunters, he says.
The titanium news isn’t all bad. The researchers found “extremely high concentrations” of titanium in the teeth. However, Wosnick says this could be the sharks’ way of ridding themselves of the element, since sharks replace their teeth more frequently than other animals.
Human food and the mining of the future
In Brazil, sharks are eaten – often by children. Theoretically, these rare earths could therefore enter humans. “All elements that are not essential to life can harm humans,” says Wosnick. Humans may also be more sensitive to the toxic effects than sharks, as mammals usually have more fat than fish. Metals tend to stick to fat and therefore accumulate more quickly.
