July 29, 2009 -- A small, fist-sized jellyfish pulsating through the water seems like an unlikely candidate to alter Earth's climate. But its motion, combined with all the swimming creatures in the sea, could stir things up enough to do exactly that, according to a new study. Scientists have wondered for over a century whether the agitations of fish, whales, plankton and jellyfish across the planet can affect ocean currents. But teasing their effect out from the powerful influences of the wind and tides has proven difficult. Kakani Katija and John Dabiri of the California Institute of Technology in Pasadena have found a clue in Jellyfish Lake, a quiet salt lake in the South Pacific archipelago of Palau. Swarms of stingless jellies migrate through the still waters there each day, providing researchers with a perfect opportunity to watch them up close as they swim. By adding dye to the water, the researchers uncovered a surprise: jellyfish move water in two ways. Their bell-shaped heads push small swirling smoke rings out behind them, as expected, but they also drag a cone of water with them wherever they go. When moving vertically, they even manage to tow denser water toward the surface. "We were expecting to see the vortex rings, but not the conical structure," Katija said. "Their body shape allows them to mix water efficiently." Related Content:
Their study will be published tomorrow in the journal Nature. Ocean mixing plays a huge role in Earth's climate. Cold water welling up from the depths and warm currents shuttling across the globe influence everything from air temperature to hurricanes. Mixing also spreads nutrients around, providing a foundation for the marine food chain. Typically, winds and tides are thought to do the lion's share of mixing. But if Katija and Dabiri's measurements apply to the open ocean, the collective motions of jellyfish, plankton, and other swimmers may be just as important. "To be able to say that these small creatures and the biosphere can participate in climate in a physical way, that's interesting," William Dewar of Florida State University in Tallahassee. "That's a novel twist on the system." The researchers' work is only a first result -- experiments will be needed to determine whether the discovery in Jellyfish Lake applies to the the world's oceans. But it poses the disturbing, if remote possibility that overfishing by humans could eventually impact Earth's climate. "It's an interesting thought exercise," Katija said. "If we take out the mixers, what's going to happen?" Related Links: HowStuffWorks.com: Ocean Currents |
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