Another consideration is microbial size. Very small microbes (less than 1 micrometer in diameter) don't align with the ocean current no matter what their shape. "These very small things don't align because they are too vigorously kicked around by water molecules in an effect called Brownian motion," said Stocker, who studies the biomechanics of the movements of ocean microbes, often in his own micro-version of a Kalliroscope called microfluidics. He recreates an ocean environment in microfluidic devices about the size of a stick of gum and uses videomicroscopy to trace and record the microbes' movements in response to food and current.
In this case, however, the research methodology was observation, followed by mathematical modeling (much of which was handled by graduate student Marcos, who created a model that coupled fluid mechanics with optics), and subsequent experimentation carried out by graduate students Mitul Luhar and William Durham using a tabletop-sized device.
But the impetus for the research was an observation of swirling microbes in a flask of water and a question posed by Justin Seymour, a former postdoctoral fellow at MIT. "Justin walked up to me with a flask of microbes in water, shook it, and asked me what the swirls were," said Stocker. "Now we know."
In addition to Seymour, who is now a research fellow at the University of Technology Sydney, other co-authors on the paper are Marcos, Luhar and Durham; Professor James Mitchell of Flinders University in Adelaide, Australia; and Professor Andreas Macke of the Leibniz Institute for Tropospheric Research in Germany.
Next steps: The researchers plan to test this mechanism in the field in a local environment suitable for experimentation, most likely a nearby lake.
|Contact: Denise Brehm|
Massachusetts Institute of Technology