A model for shear response in swimming plankton
Authored by Justin Shaw, Marek Stastna
Date Published: 2017
DOI: 10.1016/j.pocean.2016.10.012
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Mathematical description
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Abstract
Observations of zooplankton populations below their preferred light
level have been attributed to a shear response. We propose a measure of
shear based on the second invariant of the rate of strain tensor. This
quantification allows the shear response mechanism to be modelled
numerically. The importance of this mechanism is examined by modifying a
light-biased stochastic swimming model of the run and tumble type for
plankton moving in a velocity field induced by internal waves in a
channel. It is found that a model which includes the mechanisms of
settling, biased swimming, and a ``freeze in shear{''} response predicts
aggregation of plankton populations below their preferred light level, which is consistent with acoustic data observations. Depending on the
geometry of the high shear region, the population is either shifted
downward, or aggregates as a thin layer along the bottom boundary of the
high shear region. A pair of timescales is defined in order to determine
which of these two cases will occur. (C) 2016 Elsevier Ltd. All rights
reserved.
Tags
Topography
turbulence
plankton
zooplankton
Vertical migration
Nonlinear internal waves
Euphausiid euphausia-pacifica
Knight inlet
sill
Stratified flow
Solitary waves
Fluid
Individual based model (ibm)
Euphausia pacifica
Internal
waves
Shear response
Rheotaxis
Patch formation
Knight inlet