Turbulent mixing and phytoplankton life history: a Lagrangian versus Eulerian model comparison
Authored by Jeremy Baudry, Dany Dumont, Irene R Schloss
Date Published: 2018
DOI: 10.3354/meps12634
Sponsors:
National Science and Engineering Research Council of Canada (NSERC)
Platforms:
Fortran
Model Documentation:
Other Narrative
Mathematical description
Model Code URLs:
https://gitlasso.uqar.ca/dumoda01/phlag
Abstract
Phytoplankton dynamics models follow either an Eulerian or a Lagrangian
approach. The Eulerian formulation assumes that all individuals of a
population living in homogeneous environmental conditions, i.e. within a
model grid cell, are in a single average physiological state, which
generally depends on local conditions. By tracking each individual cell
or cluster of cells, the Lagrangian formulation allows population
behaviour to emerge from a broader range of individual physiological
states inherited from different life histories. In order to determine in
which mixing conditions the widely used Eulerian approach differs from a
more representative but also more computationally costly Lagrangian
formulation, we compared the results obtained from a simple
1-dimensional phytoplankton growth model using both formulations under
various mixing conditions. The chosen model is based on Droop kinetics,
where growth is a function of light and an internal nutrient cell quota.
It is applied in cases with constant and uniform diffusivity, and in
more realistic cases of wind-induced and tidal mixing. The 2 main
outcomes of our study are: (1) results from both formulations converge
in weakly stratified environments for any level of turbulent mixing, and
(2) results diverge in stratified environments and intermediate mixing
up to a diffusivity value above which the environment appears
homogeneous to moving cells, and both formulations converge. These
results suggest that in heterogeneous and dynamic marine environments,
strong variability among individuals may prevent Eulerian models from
accurately predicting phytoplankton production.
Tags
Dynamics
Light
growth
Photosynthesis
Motility
Random-walk models
Algal cells
Acclimation
Mixed-layer
Biogeochemistry
Individual based modelling
Population based modelling
Intrapopulation variability
Photoadaptation