Winds and tides aren't the only forces that move the sea: Researchers say the daily movements of sea creatures also add power to the waves. To demonstrate, they showed how "Sea-Monkeys" — the toy-store aquarium pets that are actually brine shrimp — follow variations in light to move between the surface and the depths, churning water in the process.
Oh, and the researchers used frickin' lasers for the demonstration.
Caltech engineering professor John Dabiri and graduate student Monica Wilhelmus hooked up lasers to guide the critters upward and downward through a tank of water. In the wild, Sea-Monkeys rely on sensitivity to light to tell them when to rise up and feed on algae at the surface during twilight, and then sink back down to avoid predators during the day.
"Coaxing Sea-Monkeys to swim when and where you want them to is even more difficult than it sounds," Dabiri said in a news release. "But Monica was undeterred over the course of this project and found a creative solution to a very challenging problem."
A green laser was positioned to provide a target for the shrimp (known by the scientific name Artemia salina), while a blue laser rising along the side of the tank lit up a path for the critters to follow.
The researchers filled the tank with tiny, silver-coated hollow glass spheres, each measuring less than a thousandth of an inch (13 microns) wide. The movement of the spheres was tracked using a red laser and a high-speed camera — and that showed how much energy the flapping of the Sea-Monkeys' tiny fins added to water circulation in the tank.
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Dabiri and Wilhelmus propose that billions of zooplankton follow a similar sea-churning pattern every day — and they figure that all that movement could add as much as a trillion watts of power to drive ocean circulation. In comparison, they estimate the combined energy input from the winds and tides at 2 trillion watts.
In previous work, Dabiri proposed that jellyfish movements could add to ocean circulation, playing a vital role in stirring up the sea's nutrients and distributing heat.
"Now, these new lab experiments show that similar effects can occur in organisms that are much smaller but also more numerous — and therefore potentially more impactful in regions of the ocean important for climate."
It's a conceptual leap to go from a tankful of Sea-Monkeys to oceans filled with plankton, and some oceanographers are skeptical of the claim that the movements of organisms contribute significantly to ocean circulation. But few would disagree with the bottom line: Tiny critters can have a huge impact on the biosphere.
A paper describing the experiment, "Observations of Large-Scale Fluid Transport by Laser-Guided Plankton Aggregations," is published in the journal Physics of Fluids. The research was supported by the U.S.-Israel Binational Science Foundation, the Office of Naval Research, and the National Science Foundation.