Phytoplankton social mixers

Tiny ocean plants use turbulence for travel to social gatherings. Tiny ocean plants, or phytoplankton, were long thought to be passive drifters in the sea - unable to defy even the weakest currents, or travel by their own volition. In recent decades, research has shown that many species of these unicellular microorganisms can swim, and do so to optimize light exposure, avoid predators or move closer to others of their kind. Now scientists at MIT and Oxford University have shown that the motility of phytoplankton also helps them determine their fate in ocean turbulence. Rather than acting to distribute them evenly - as physics would demand of small particles mixed into a fluid - the individual vortices that make up ocean turbulence are like social mixers for phytoplankton, bringing similar cells into close proximity, potentially enhancing sexual reproduction and other ecologically desirable activities. In a paper appearing online July 15 in Nature , William Durham of Oxford, Roman Stocker of MIT and co-authors describe how at the scale of millimeters, phytoplankton caught in a watery vortex form highly concentrated patches at the center of the swirl. In the turbulent ocean where short-lived vortices form continually, this process repeats itself, carrying the microorganisms from social mixer to social mixer.