The Jellyfish Effect

29 July 2009
Posted by Chris Smith.

You may have heard of the butterfly effect where the theory is that the tiny swirls of air moved by a butterfly's wings go on to affect event after event, leading up to a much larger event like a hurricane. Well now it seems that we need to coin a new phrase: "the jellyfish effect." A study in Nature this week has found that jellyfish, along with other marine creatures, significantly contribute to ocean turbulence. 

When you think of ocean turbulence your first thought might be winds or tides as major factors. In terms of size and force these two seem like pretty strong contenders. To test how much of an effect jellyfish had Kakani Katija and John Dabiri from the California Institute of Technology measured the amount of fluid mixing caused by jellyfish as they went about their business in the sea. And they did this using a new bit of technology: scuba-based laser velocimetry which uses laser light to follow the changes in movement of water. The researchers found that a theory developed by Sir Charles Darwin actually described the effect of these jellyfish quite well.

Sir Charles Darwin was in fact the grandson of the more famous evolutionary biologist but he came up with a theory which described how the shape and size of a marine animal are important in ocean mixing. And that's what Katija and Dabiri found. Based on these velocimetry measurements they calculated how much of an effect all of the jellyfish in the ocean might have and it was actually quite a big number: 10^12W per unit of time - the same order of magnitude as the winds and tides. It wasn't only jellyfish responsible for the mixing either, even zooplankton have a part to play.

Jellyfish aggregation around Kakani KajiraThis all means that a change in the abundance of marine life or even changes in biodiversity could have major implications for ocean mixing, which is quite important for marine life itself. The researchers also point out that ocean mixing could play a role in carbon sequestration. There are huge amounts of carbon out there, locked up under the sea and we don't know if these fluid movements caused by the jellyfish are partly responsible for maintaining that downward transport of carbon.

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