They may be small, but sea monkeys, which are actually a type of shrimp, can move ocean currents with the same force that winds and tides do, according to a new study.
Like other zooplankton, brine shrimp (Artemia salina) move up and down in the ocean in large groups in response to changing light conditions, coming closer to the surface at night and retreating to deeper waters during the day. This collective movement mixes seawater so strongly that researchers suggest small marine organisms could affect global ocean circulation patterns on a level comparable to the wind and the tides.
"This was the first hint that animals could transport water over distances much longer than their body size," study co-author John Dabiri, an engineer studying biological physics at the California Institute of Technology (Caltech), told National Geographic.
To get a better sense of their churning powers, Dabiri and colleague Monica Wilhelmus, also at Caltech, examined these playful sea monkeys - so named for their monkey-like tails - in a special aquarium equipped with lasers.
Described in the journal Physics of Fluids, a blue laser rising along the side of the tank triggered upward migration while a green laser in the middle of the tank kept the swimming shrimp centered in a group, similar to how they stick together in the ocean. By seeding the water with silver-coated, hollow glass spheres, the researchers could see the changing currents with a high-speed camera.
They saw that the tiny shrimp - just 0.2 inches (5 millimeters) long - could change the ocean's circulation in swirls bigger than themselves with a power of about a trillion watts, or terawatts.
"This research suggests a remarkable and previously unobserved two-way coupling between the biology and the physics of the ocean: the organisms in the ocean appear to have the capacity to influence their environment by their collective swimming," Dabiri said in a statement.
Usually the winds and tides alone are credited with creating currents that churn the ocean's salt, nutrients and heat, but the results indicate that microscopic animals also influence currents.
Dabiri and Wilhelmus hope to apply their work on a larger scale in the ocean, focusing on other important kinds of vertically migrating animals such as krill and copepods.