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Jellyfish stir up the Ocean

7.31.09 - Small ocean animals like jellyfish stir up the oceans of the world in the same magnitude as winds and tides. The movements of jellyfish contribute significantly to the mixing of water. This is what the scientist Kakani Katija from the California Institute of Technology in Pasadena found out.

Like the air that we breathe which is constantly moving the water in the ocean never rests. The amounts of water in our oceans are permanently moving so that temperature, nutrition and gases inside get distributed all the time. Until recently, the belief was that the contribution of animals in this process was rather small. The viscosity of the water would not allow the movement of animals travel too far.

Kakani Katija's study now shows that this assumption was incorrect and that the movement of animals helps significantly in stirring up our oceans. An all-but forgotten contribution of Sir Charles Darwin - physicist grandson of the Charles Darwin - has resolved a long-standing debate about ocean mixing. He suggested, in 1953, a mechanism that enables swimming animals to contribute significantly to the mixing of water in the ocean. 'Darwinian' mixing is different, and occurs when a solid body travelling in a fluid sets a portion of the surrounding fluid into motion so that it propagates along with the body.

Kakani Katija and John Dabiri used field measurements of jellyfish swimming in a remote island lake, combined with a new theoretical model, to demonstrate that the contribution of living organisms to ocean mixing via this mechanism is substantial.

Not the size of the wave movements, that the animals created, but simply the form seems to play a critical role in the mixing process, reported the scientists. In addition to that the viscosity of the water seems to increase the process rather than slowing it down.

To proof their theory the scientists used a pipette to put color in front of swimming jellyfish to visualize the water movements as the jellyfish swims through it. The experiment showed that jellyfish pretty much haul amounts of water behind them and that the water follows them several swim cycles.

So far the data that the researchers have are based on the measurements of the individual experiments that they have done thus far. The next step is to simulate the movements of the water based on all the various effects on a computer, explained the scientists.

To learn more about ocean animals watch our free class on Ocean Animals that was taken at the Monterey Bay Aquarium in California.

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