Jellyfish Have Big Mixing Effect On The Oceans

Pulsating jellyfish and their swim pals stir up the oceans with as much vigor as tides and winds, scientists have found. Their study also found that the shape of the aquatic blobs affects their mixing abilities.

Until now, oceanographers had dismissed the idea that such tiny ocean creatures could play a role in mixing various layers of ocean water on a large scale. The argument was based on evidence that any swishing from fish tails, say, would get dampened by the ocean's viscosity (a measure of a fluid's resistance to flow — honey has a high viscosity compared with water).

But the new study, which is published in the July 30 issue of the journal Nature, reveals a mixing mechanism first described by Charles Darwin's grandson that is actually enhanced by the ocean's viscosity, making these tiny sea critters major players in ocean mixing.

"We've been studying swimming animals for quite some time," said John Dabiri, a Caltech assistant professor of aeronautics and bioengineering. "The perspective we usually take is that of how the ocean — by its currents, temperature, and chemistry — is affecting the animals. But there have been increasing suggestions that the inverse is also important — how the animals themselves, via swimming, might impact the ocean environment."