TITLE: Ecology and Geochemistry of Planktonic Foraminifera

SUPERVISOR & CO-SUPERVISOR(S)
Corinne Le Quéré (UEA and BAS)
Mack Chapman (UEA)
Karen K. Kohfeld (School of Earth and Environmental Sciences, Queens College, New York)

Phd to be held either at the University of East Anglia (UEA) or at the British Antarctic Survey (BAS)

PROJECT DESCRIPTION

The distribution and geochemistry of planktonic foraminifera make up an important component of the marine sediment archive of past changes in oceanic conditions. Correct interpretation of the fossil record left by planktonic foraminifera in terms of oceanographic characteristics requires an understanding of the modern ecology, life cycle and shell calcification processes in planktonic foraminifera. To date, foraminiferal studies have used inverse statistical techniques such as transfer functions and empirical geochemical correlations in order to translate geological foraminiferal data into climatic parameters (e.g., sea^Ösurface temperature). These studies have frequently relied upon the oversimplification of the processes controlling planktonic foraminifera in order to reconstruct only one climate parameter at the expense of the other variables.

The proposed project involves the creation of a process-based forward model that simulates the response in foraminiferal distributions and stable isotope chemistry to a suite of environmental parameters. The simulated changes in foraminiferal distributions and geochemistry can then be compared with the sedimentary record, and used as an off-line validation tool for ocean biogeochemistry models. It time allows, this same method could be applied to other plankton species (diatoms, dinoflagellates and radiolaria).

Various oceanographic parameters have been shown to be important in determining the composition of foraminiferal assemblages, including (a) temperature (b) thermocline and halocline structure (depth of mixed layer) (c) sea-ice extent (surface stratification) (d) seasonality and intensity of upwelling and phytoplankton blooms. The stable isotope composition of planktonic foraminifera is influenced by ambient seawater and TCO2 isotope composition, but it will also be influenced by foraminiferal habitat which is partially governed by thermocline structure. Furthermore, disequilibrium effects associated with temperature, carbonate chemistry and the isotopic composition of food source will influence the stable isotope composition. These oceanographic characteristics are of primary importance between approximately 0 and 300 m, although carbonate dissolution processes in deep waters will also influence the presence, absence of foraminifera, and the preferential dissolution of certain species.

Several laboratory, plankton tow, sediment trap and surface sediment studies have been completed and provide initial information about the processes that control the distribution and fluxes of the ~30 extant species / morphotypes of planktonic foraminifera. Laboratory studies have also focussed on what controls the stable isotope and trace metal geochemistry of approximately 3-4 key species (e.g. G. bulloides, O. universa, and G. sacculifer). These studies could serve as a basis for establishing the initial relationships between ocean conditions and foraminiferal response, and the project will require a synthesis of information from these studies.

Several geological datasets are already present and could serve as validation for this type of model. A global database of foraminiferal distributions for the modern and last glacial oceans is archived as part of NOAA-NGDC. These data are currently available as percentages and not as absolute fluxes, although absolute species fluxes could be compiled from sediment trap studies for interannual comparisons, and total carbonate fluxes are available on glacial-interglacial time scales. Also included in this archive are regional-to-global compilations (e.g. S. Atlantic) of stable isotope geochemistry of various species for the same time periods.

This work will be undertaken in the framework of the Dynamic Green Ocean Project (http://www.bgc-jena.mpg.de/bgc_prentice/projects/green_ocean/start.html), an international project aimed at developing a community model of ocean biogeochemistry for applications to Earth system problems. Acceptable degree(s) of applicants (please tick preferred subjects):

This Studentship may be eligible for support to non-UK residents under the ~SFAASIS~T (~SFellowships in Antarctic Air-Sea-Ice Science~T) Marie Curie Early Stage Training Network: a joint venture of the University of East Anglia and the British Antarctic Survey. UK residents may be eligible for funding from other sources (e.g. Natural Environment Research Council).

To apply, go through the studentship web page of the School of Environment University of East Anglia, http://www.uea.ac.uk/env/studentships/faasis/faasis.htm