TITLE: the role of diatoms in the Antarctic carbon cycle.
PhD project of Sophie Chollet

SUPERVISOR & CO-SUPERVISORS
Erik Buitenhuis (UEA and BAS), Gill Malin (UEA), Corinne Le Quéré (UEA and BAS)

Phd funded by the School of Environmental sciences, University of East Anglia (UEA) and the National Environmental Research Council (NERC)

PROJECT DESCRIPTION

Diatoms are major players in the global carbon cycle. They are a dominant part of the microphytoplankton size fraction (> 20 um), responsible for about 30% of the oceanic chlorophyll inventory and dominate the export of organic matter from surface waters to the deep ocean (Raven & Waite 2004, Uitz et al. 2006). Thus understanding the role of diatoms in export and air-sea CO₂ exchange is an important goal of biogeochemical models.

Sarthou et al. (2005) made a synthesis of diatom data for maximum growth rate as a function of cell volume, photosynthetic parameters, nutrient limitation of uptake rates, elemental composition and loss terms. This shows that whilst the importance of diatoms has been recognised for a long time, there is relatively little information about basic diatom physiology for example: growth rate as a function of temperature, exudation of dissolved organic carbon and light physiology. Such information is needed to parameterise models.

In this PhD project we intend to extend this synthesis to the temperature dependence of growth rate, production of DOC, and light limitation of growth rate. The focus will be the Southern Ocean where diatoms are key players in the carbon cycle, but with the inclusion of temperate and sub-tropical species for comparative purposes. A combination of literature study, laboratory experiments and modelling will be required. Hypotheses about ecosystem functioning and the effects and feedbacks on global change across the Southern Ocean will be tested and comparison will be made with large scale satellite chlorophyll data sets. The student will refine the Dynamic Green Ocean Model (Le Quéré et al. 2005, Buitenhuis et al 2006) to improve the representation of biogeochemical fluxes mediated by diatoms.

References and reading list for this project