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Science 20 February 2009:
Vol. 323. no. 5917, pp. 1067 - 1070
DOI: 10.1126/science.1167334
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Reports

Disruption of Vertical Motility by Shear Triggers Formation of Thin Phytoplankton Layers

William M. Durham,1 John O. Kessler,2 Roman Stocker1*

Thin layers of phytoplankton are important hotspots of ecological activity that are found in the coastal ocean, meters beneath the surface, and contain cell concentrations up to two orders of magnitude above ambient concentrations. Current interpretations of their formation favor abiotic processes, yet many phytoplankton species found in these layers are motile. We demonstrated that layers formed when the vertical migration of phytoplankton was disrupted by hydrodynamic shear. This mechanism, which we call gyrotactic trapping, can be responsible for the thin layers of phytoplankton commonly observed in the ocean. These results reveal that the coupling between active microorganism motility and ambient fluid motion can shape the macroscopic features of the marine ecological landscape.

1 Department of Civil and Environmental Engineering, Massachusetts Institute of Technology (MIT), Cambridge, MA 02139, USA.
2 Department of Physics, University of Arizona, Tucson, AZ 85721, USA.

* To whom correspondence should be addressed. E-mail: romans{at}mit.edu

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
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S. A. Amin, D. H. Green, M. C. Hart, F. C. Kupper, W. G. Sunda, and C. J. Carrano (2009)
PNAS 106, 17071-17076
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