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<DIV><FONT face=Arial size=2>Marine Ecology<BR>Volume 30 Issue 2, Pages 133 -
150<BR>Published Online: 21 Apr 2009<BR></FONT></DIV>
<DIV><FONT face=Arial size=2><FONT size=4>Turbulence-plankton interactions: a
new cartoon</FONT><BR>Peter A. Jumars 1 , John H. Trowbridge 2 , Emmanuel Boss 1
& Lee Karp-Boss 1 <BR> 1 School of Marine Sciences, University of
Maine, Orono, ME, USA <BR> 2 Applied Ocean Physics & Engineering
Department, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
<BR>Correspondence to Peter A. Jumars, Darling Marine Center, University of
Maine, 193 Clark's Cove Road, Walpole, ME 04573, USA. E-mail:
jumars@maine.edu<BR> <BR><BR><STRONG>ABSTRACT</STRONG><BR>Climate change
redistributes turbulence in both space and time, adding urgency to understanding
of turbulence effects. Many analytic and analog models used to simulate and
assess effects of turbulence on plankton rely on simple Couette flow. There
shear rates are constant and spatially uniform, and hence so is vorticity. Over
the last decade, however, turbulence research within fluid dynamics has focused
on the structure of dissipative vortices in space and time. Vorticity gradients,
finite net diffusion of vorticity and small radii of curvature of streamlines
are ubiquitous features of turbulent vortices at dissipation scales but are
explicitly excluded from simple, steady Couette flows. All of these flow
components contribute instabilities that cause rotation of particles and so are
important to simulate in future laboratory devices designed to assess effects of
turbulence on nutrient uptake, particle coagulation, motility and predator-prey
encounter in the plankton. The Burgers vortex retains these signature features
of turbulence and provides a simplified "cartoon" of vortex structure and
dynamics that nevertheless obeys the Navier-Stokes equations. Moreover, this
idealization closely resembles many dissipative vortices observed in both the
laboratory and the field as well as in direct numerical simulations of
turbulence. It is simple enough to allow both simulation in numerical models and
fabrication of analog devices that selectively reproduce its features. Exercise
of such numerical and analog models promises additional insights into mechanisms
of turbulence effects on passive trajectories and local accumulations of both
living and nonliving particles, into solute exchange with living and nonliving
particles and into more subtle influences on sensory processes and swimming
trajectories of plankton, including demersal organisms and settling larvae in
turbulent bottom boundary layers. The literature on biological consequences of
vortical turbulence has focused primarily on the smallest, Kolmogorov-scale
vortices of length scale η. Theoretical dissipation spectra and direct numerical
simulation, however, indicate that typical dissipative vortices with radii of 7η
to 8η, peak azimuthal speeds of order 1 cm s−1 and lifetimes of order 10 s or
longer (and much longer for moderate pelagic turbulence intensities) deserve new
attention in studies of biological effects of
turbulence.</FONT></DIV></BODY></HTML>