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RESEARCH ARTICLE
Contents Vol 58(10)

The effect of packaging of chlorophyll within phytoplankton and light scattering in a coupled physical–biological ocean model

Mark E. Baird A B , Patrick G. Timko A and Lujia Wu A
+ Author Affiliations
- Author Affiliations

A Climate Change Research Centre, School of Mathematics and Statistics, University of New South Wales, Sydney, NSW 2052, Australia.

B Corresponding author. Email: m.baird@unsw.edu.au

Marine and Freshwater Research 58(10) 966-981 https://doi.org/10.1071/MF07055
Submitted: 18 June 2007  Accepted: 14 September 2007   Published: 31 October 2007

Abstract

A coupled physical–biological model forced with spectrally resolved solar radiation is used to investigate the effect of packaging of pigment and light scattering on physical and biological properties in the open ocean. Simulations are undertaken with three alternate formulations of vertical attenuation, which consider: (1) chlorophyll as dissolved in the water column; (2) chlorophyll packaged into phytoplankton cells with no scattering; and (3) packaged chlorophyll with scattering. In the coupled model, depth-resolved solar heating depends on the vertical profile of phytoplankton concentration, creating a feedback mechanism between the physical and biological states.

The particular scenario investigated is a northerly wind off the coast of south-east Australia. The packaging of chlorophyll approximately halves the attenuation rate of 340–500 nm light and a phytoplankton maximum forms ~10 m deeper than in the dissolved chlorophyll case, with a corresponding adjustment of the dissolved inorganic nitrogen and zooplankton fields. Scattering approximately doubles the vertical attenuation of 340–600 nm light, lifting the phytoplankton maximum by ~10 m when compared with the packaged chlorophyll case. Additionally, strong horizontal gradients in chlorophyll distribution associated with filaments of upwelled water inshore of the East Australian Current, when modelled with alternate formulations of vertical light attenuation, result in circulation changes. The explicit representation of the packaging of pigment and light scattering is worth considering in coupled physical–biological modelling studies.

Additional keywords: biological induced heating, East Australian Current, light scattering, package effect, Port Stephens.


Acknowledgements

This research was funded by ARC Discovery Projects DP0557618 held by MB and DP0208663 held by Jason Middleton (UNSW). Analysis of the model output for a lower resolution configuration was undertaken in partial fulfilment of Lujia Wu’s Honours thesis at the UNSW. The use of the Australian Partnership for Advanced Computing (APAC) supercomputer, is gratefully acknowledged. We thank Alan Blumberg and George Mellor for the free availability of the Princeton Ocean Model (POM), and Patrick Marchesiello and Peter Oke for earlier work on the POM configuration for the waters off south-east Australia.


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