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Filter feeders and plankton increase particle encounter rates through flow regime control

Humphries, Stuart


Stuart Humphries


Collisions between particles or between particles and other objects are fundamental to many processes that we take for granted. They drive the functioning of aquatic ecosystems, the onset of rain and snow precipitation, and the manufacture of pharmaceuticals, powders and crystals. Here, I show that the traditional assumption that viscosity dominates these situations leads to consistent and large-scale underestimation of encounter rates between particles and of deposition rates on surfaces. Numerical simulations reveal that the encounter rate is Reynolds number dependent and that encounter efficiencies are consistent with the sparse experimental data. This extension of aerosol theory has great implications for understanding of selection pressure on the physiology and ecology of organisms, for example filter feeders able to gather food at rates up to 5 times higher than expected. I provide evidence that filter feeders have been strongly selected to take advantage of this flow regime and show that both the predicted peak concentration and the steady-state concentrations of plankton during blooms are ≈33% of that predicted by the current models of particle encounter. Many ecological and industrial processes may be operating at substantially greater rates than currently assumed.


Humphries, S. (2009). Filter feeders and plankton increase particle encounter rates through flow regime control. Proceedings of the National Academy of Sciences of the United States of America, 106(19), 7882-7887.

Journal Article Type Article
Acceptance Date Mar 26, 2009
Online Publication Date Apr 28, 2009
Publication Date May 12, 2009
Deposit Date Nov 13, 2014
Journal Proceedings Of The National Academy Of Sciences Of The United States Of Ame
Print ISSN 0027-8424
Electronic ISSN 1091-6490
Publisher National Academy of Sciences
Peer Reviewed Peer Reviewed
Volume 106
Issue 19
Pages 7882-7887
Keywords Biological fluid dynamics; Coagulation; Phytoplankton; Suspension feeding
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