The fact that ocean currents, which move the waters and help mix-up varying temperatures, salinity and nutrients, are caused by tides and winds is a well-documented fact. Now some researchers from the California Institute of Technology believe that the zillions of small marine animals that live deep inside our oceans also play a big role in the churning of the waters.
Caltech's fluid dynamics expert John Dabiri, who published his findings in the October 2014 edition of the Physics of Fluids, says that while researching jellyfish in 2009, he and colleague discovered that the sticky animals drag along with them, a halo of water much larger than the size of their tiny bodies. This led him to wonder if the jellyfish and the other microscopic sea creatures, collectively known as zooplankton, are responsible for moving huge amounts of water as they swim up and down the ocean, in packs of billions.
To test the theory, he teamed up with graduate student Monica Wilhelmus, to conduct an experiment in the laboratory. While krill would have been ideal for the test, the tiny organisms don't do well in laboratory settings. Hence, the researchers had to settle for brine shrimp (sea monkeys), which while not a member of the migrating zooplankton, have swimming patterns that are similar to krill.
In order to emulate a migration, the researchers began by building an automated laser robot that beamed moving blue light through a tank filled with thousands of sea monkeys. The tiny brine shrimp, that are highly attracted to light, followed the beam all the way to the top. As they swam, they kicked back water behind them. While each tiny animal could not do much individually, together, they were able to create large enough ripples or eddies to move the tank waters.
After conducting several such trials and measuring the impact, Dabiri and his partner concluded that the billions of zooplankton that migrate up and down the ocean water each day, possibly add as much as a trillion watts of power, to drive ocean circulation. Given that the combined energy from winds and tides is estimated to add about 2 trillion watts, this means that the tiny zooplankton are an equally potent force in tide creation.
But not everyone is convinced that such is the case. Christian Noss an environmental physicist at Germany's University of Koblenz-Landau believes that the laboratory effect does not extend to the open seas. That's because thanks to the differences in temperature and salinity, ocean waters are stratified. This means that the less dense, warmer water floats on top, while the heavier, colder water tends to sink at the bottom. He asserts that this mitigates the mixing effect produced by these animals because even collectively, they do not have enough strength to drag up large amounts of the heavier water. The scientist's conviction is not just based on theory, but also on an experiment that he conducted, using a tiny crustacean called Daphnia in stratified water.
Dabiri and Monica, plan to continue their research by conducting further experiments in stratified water and also in the open oceans. If the researchers theory is accurate, it may help scientists model climate change more accurately. That's because the ocean is responsible for absorbing over a quarter of the carbon dioxide emitted by human activity and a lot of it may be due to the constant efficient churning by these tiny sea animals.