Swimming for survival: a role of phytoplankton motility in a stratified turbulent environment

Ross, O. N.; Sharples, J.. 2008 Swimming for survival: a role of phytoplankton motility in a stratified turbulent environment. Journal of Marine Systems, 70 (3-4). 248-262. 10.1016/j.jmarsys.2006.07.008

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Abstract/Summary

We investigate a role for vertical migration in stratified coastal water, where the swimming speed is generally significantly less than the typical turbulent fluctuations in a tidally-mixed bottom layer. In our modelling approach we use a k-epsilon turbulence model to describe the physical forcing, a Lagrangian random walk model to describe the vertical displacement of individual cells in response to turbulence and due to cell motility, and a phytoplankton growth model to direct the swimming behaviour of the phytoplankton according to their light and nutrient requirements. The model results show how the cells form a stable subsurface chlorophyll maximum (SCM) at the base of the thermocline where episodic tidal turbulence causes erosion of part of the SCM biomass into the bottom mixed layer (BML). We then focus on the question of whether an ability to swim (weakly, compared to typical bottom layer turbulent intensities) provides any advantage by allowing return to the SCM. Our results show that tidal turbulence in the BML helps both motile and neutrally-buoyant cells by periodically pushing them into the base of the thermocline. Motile cells then have the advantage that they can swim further into the thermocline towards higher light which also reduces the likelihood of being remixed back into the BML

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1016/j.jmarsys.2006.07.008
Programmes:	Oceans 2025 > Shelf and coastal processes
ISSN:	0924-7963
Additional Keywords:	PHYTOPLANKTON MOTILITY; TIDAL MIXING; SHELF SEAS; PHOTOTAXIS; THERMOCLINE; TURBULENCE MODELLING; LAGRANGIAN MODELLING; RANDOM WALK MODELS; VERTICAL DISTRIBUTION; CLOSURE MODEL; WATER COLUMN; MIGRATION; SIMULATION; SUCCESSION; DYNAMICS; LAYER; SEA ECHO
NORA Subject Terms:	Marine Sciences
Date made live:	16 Feb 2009 12:40 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/5418

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