NERC quota PhD studentship proposal
TITLE
Investigation of Antarctic climate of the past 200 years using the annual growth
increments in the shell of the bivalve mollusc Yoldia eightsi
SUPERVISOR(S):
Dr Paul Butler (SOS, Bangor), Professor James Scourse (SOS, Bangor), Professor
Lloyd Peck (BAS), Professor Ian Hall (Cardiff University)
COLLABORATION/CASE PARTNERS:
British Antarctic Survey / School of Earth and Ocean Sciences, Cardiff University
BACKGROUND/CONTEXT OF PROJECT (max 300 words)
The scarcity of long instrumental series from the Southern Ocean is limiting our
understanding of key feedbacks within the Antarctic system, including the timing of onset and
subsequent evolution of the recent rapid warming in the West Antarctic Peninsula. A pilot
study based on the sclerochronology of the common Antarctic mollusc Yoldia eightsi has
shown that it can constitute a viable annually-resolved shell-based proxy archive for Antarctic
coastal waters. Links have been found between growth patterns in a Y. eightsi chronology
and sea surface temperatures, phytoplankton bloom activity and fast-ice duration. With
access to adequate shell material and research time it will be possible to construct annuallyresolved chronologies spanning at least two hundred years and possibly even longer. It will
then be possible to use the growth increment indices and the associated geochemical data to
provide proxies for environmental changes that occurred well before the beginning of
instrumental observations. In addition, radiocarbon analysis of absolutely-dated shell
material could be used to calibrate the marine radiocarbon reservoir in the Southern Ocean,
with consequent benefits for the dating accuracy of other marine proxies in the area and
improved understanding of regional ocean circulation.
An endogenous growth signal found during the Yoldia eightsi pilot study suggests that
additional biological information (e.g. spawning events, endogenous metabolic cycles) can be
extracted from growth patterns in the mollusc’s shell. Further research into this effect,
comparing Y. eightsi from different sites and other bivalve species from different latitudes
might provide new insights into longevity and ontogenetic growth cycles in marine molluscs,
thus helping to isolate environmental drivers from endogenous effects with greater precision.
AIMS AND OBJECTIVES (max 200 words)
1. Extension of the existing Y. eightsi chronology back in time using subfossil
specimens currently being sourced by BAS. The initial aim would be to extend it
back for 200 years.
2. Extension of the chronology forward in time from its present end date of 1988 to
allow improved calibrations with more recent instrumental measurements (including
SST, fast-ice duration and phytoplankton bloom dynamics).
3. Geochemical analysis of stable isotopes and trace elements in the Y. eightsi shell to
identify seasonal signals, bottom water temperatures (δ18Oshell) and food sources
(δ13Cshell).
4. Investigation of geochemical methods for determining δ18Owater so that an
unambiguous interpretation can be made of δ18Oshell as a temperature proxy. These
may include clumped isotopes, δD of the shell organic matrix or Na/Cashell.
5. Investigation of the marine radiocarbon reservoir age through radiocarbon dating of
absolutely-dated shell material.
6. Further study of the endogeneous growth cycle using samples of Y. eightsi from
different sites and depths. These would be compared with equivalent endogeneous
growth patterns in other species of bivalve mollusc from Antarctica and other parts of
the world.
7. Study of the recruitment and population structure of Yoldia eightsi.
8. Assessment of other Antarctic species (eg Laternula elliptica) for their potential as
sclerochronological proxy archives.
MATERIALS/METHODS/TRAINING
ELEMENT
(max
200
words)
Shell processing equipment and imaging software for the visualization and measurement of
increments are available at SOS Bangor. Shells of Y. eightsi and other Antarctic bivalves will
be sourced by BAS. Other (non-Antarctic) shells are curated at Bangor. Geochemical
analyses will be carried out at Cardiff, subject to specific funding being applied for. The
student will receive training in crossdating and crossmatching of growth increments,
chronology construction and statistical calibration of the chronology with instrumental
measurements. The student will benefit from collaboration with staff within the
sclerochronology group and with analytical geochemists at British Antarctic Survey and
Cardiff University. All PhD students at Bangor undertake a range of approved transferable
skill modules during their first year and students’ presentational skills are developed through
seminar programmes run by the School of Ocean Sciences and College of Natural Sciences.
COSTS (max 100 words)
There will be small costs associated with the purchase of chemicals, resin and slides for the
shell sectioning (total costs <£300). Other costs, including geochemical analyses and
fieldwork in Antarctica will be funded by separate applications to appropriate NERC
committees.