Author: Carolyn Gramling / Source: Science News
When it comes to tiny ocean swimmers, the whole is much greater than the sum of its parts.
Ocean turbulence stirred up by multitudes of creatures such as krill can be powerful enough to extend hundreds of meters down into the deep, a new study suggests.Brine shrimp moving vertically in two different laboratory tanks created small eddies that aggregated into a jet roughly the size of the whole migrating group, researchers report online April 18 in Nature. With a fluid velocity of about 1 to 2 centimeters per second, the jet was also powerful enough to mix shallow waters with deeper, saltier waters. Without mixing, these waters of different densities would remain isolated in layers.
The shrimp represent centimeter-sized swimmers, including krill and shrimplike copepods, found throughout the world’s oceans that may together be capable of mixing ocean layers — and delivering nutrient-rich deep waters to phytoplankton, or microscopic marine plants, near the surface, the researchers suggest.
TINY SWIMMERS
“The original thinking is that these animals would flap their appendages and create little eddies about the same size as their bodies,” says John Dabiri, an expert in fluid dynamics at Stanford University. Previous work, including acoustic measurements of krill migrations in the ocean (SN: 10/7/06, p. 238) and theoretical simulations of fluid flow around swimmers such as jellyfish and shrimplike copepods (SN: 8/29/09, p. 14), had suggested that they may be stirring up more turbulence than…
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