Creatures large and small may play an important role in the stirring of ocean waters, according to a study released on Thursday that confirms a theory advanced by Charles Darwin.
So-called ocean mixing entails the transfer of cold and warm waters between the equator and poles, as well as between the icy, nutrient-rich depths and the Sun-soaked top layer. It plays a crucial part in marine biodiversity and, scientists now suspect, in maintaining Earth’s climate.
In the mid-19th century, Darwin - best known as the father of evolutionary theory - proposed that fish and other sea swimmers might somehow contribute significantly to currents as they moved forward. But this was dismissed by modern scientists as a fishy story.
In 1960s, experiments compared the wake turbulence created by sea creatures with overall ocean turbulence. They showed that the whirls kicked up by microscopic plankton or even fish quickly dissipated in dense, viscous water.
On this evidence, sea creatures seemed to contribute nothing to ocean mixing. The clear conclusion was that the only drivers of note were shifting winds and tides, tied to the gravitational tug-of-war within our Solar System.
But the new study, published in the British science journal Nature, goes a long way toward rehabilitating Darwin and his fellow Victorians, and uses the quiet pulse of the jellyfish to prove the case.