Despite their size, the ocean's plant plankton are crucial to much of life on Earth. Plankton are the foundation of the marine food web, produce half the world's oxygen and suck up harmful carbon dioxide.
According to a study published Jul. 28 in the journal Nature, plankton levels in the oceans worldwide are down 40 percent since the 1950s, and the probable cause, the study says, is global warming, which makes it hard for the plant plankton to get vital nutrients.
The numbers are both staggering and disturbing, say the Canadian scientists who did the study and a top U.S. government scientist.
"It's concerning because phytoplankton is the basic currency for everything going on in the ocean," said Dalhousie University biology professor Boris Worm, a study co-author. "It's almost like a recession ... that has been going on for decades."