A group of German scientists tested the effects of a more acidic ocean on sharks’ teeth and found that future generations of sharks could have weaker teeth because of changing ocean chemistry.

It was quite a discovery in tropical waters to bring in a Greenland shark, which can live for more than 500 years, according to the National Oceanic and Atmospheric Administration.

According to one study, people are responsible for the deaths of about 100 million sharks a year. For Shark Awareness Day, take a look at some other surprising shark facts. For example, they feed on animals such as sea turtles, who consume huge amounts of sea grass. But that's a hard job to do when humans kill sharks in astronomical numbers. Humans, while lacking the 7 rows of teeth, are still worseFor every human killed in a shark attack, humans kill an estimated 2 million sharks.