SAGES PhD Studentship Proposal
Secrets from a Deep Reef: Structure, Biogeography and Palaeoclimate
Reconstruction from Mingulay Reef Complex Sediment Cores.
Dr Daniel Sinclair (Scottish Association for Marine Sciences): dan.sinclair@sams.ac.uk
Mr David Long (British Geological Survey): dal@bgs.ac.uk
Dr Mary Elliot (University of Edinburgh): mary.elliot@glg.ed.ac.uk
Dr J. Murray Roberts (Scottish Association for Marine Sciences): Robertsjm@uncw.edu
This project is to be funded by SAGES, with matching funds from the BGS.
Deep Coral Reef Structure, Geology and Biogeography
Although deep corals have been known since the time of Linnaeus [1], their ability to
build extensive, beautiful and complex reefs has only recently been discovered [2], and
little is known about their formation and structure [3]. In 2003 large Lophelia pertusa
reefs were found off the west coast of Scotland [4], and in October 2007 the British
Geological Survey gathered a series of vibrocores through the active Mingulay Reef
complex (Figure 1).
The chance to look inside the structure of these reefs gives us a unique opportunity
to answer a number of important questions about reef structure and growth: When was
the reef established, and how rapidly does it grow? Has growth been continuous and if
so, how did the coral cope with the rapid climate fluctuations during the Loch Lomond
stadial? Is there evidence for changes in species or coral morphology throughout these
times? How effectively and efficiently does the reef trap sediments, and are they
stratigraphically continuous or comprehensively re-worked by currents and deep
wave/tide action? How rapidly are individual coral fragments degraded, and by what
processes? All of these questions can be addressed through classical sediment
stratigraphy/petrography techniques and radioisotope dating of sediments and coral
fragments [e.g. 5].
Palaeoceanography and Palaeoclimate Reconstruction
Sediment cores are routinely used for palaeoclimate reconstruction using calcareous
micro fossils, and we will extract records of temperature and salinity from analysis of
18O and Mg/Ca in Foraminifera from the Mingulay cores. However, the cores offer
another very exciting possibility: they contain a dense mesh of coral fragments and
sediment, possibly in a chronological sequence dating back to the initiation of reef
growth sometime after deglaciation began 18,000 years ago. In the last few years, a
significant amount of work has been conducted in order to establish the use of Lophelia
for palaeoceanographic reconstruction [6-10], and the Mingulay cores represent an ideal
opportunity to now put these techniques into practice.
Corals are ideal for U-series dating while Sr/Ca and Mg/Ca ratios allow
palaeotemperature reconstruction on sub-seasonal timescales [6]. Parallel 14C and Useries dating allows the study of C-ventilation histories [11, 12] while bulk-skeleton
oxygen isotopes may preserve palaeosalinity information. Phosphorus and barium
potentially record nutrient fluxes, while trace metals reflect changing oceanic chemistry
[7, 9]. Novel stable isotope systems (Sr, Li, Ca) are also being developed and applied to
palaeoceanographic studies [13].
Mingulay reef is a dynamic environment (Figure 2), and study of these samples
offers excellent opportunities for developing and expanding our knowledge of North
Atlantic oceanography. The corals are bathed in high salinity Atlantic Ocean waters [14],
Deep Reef Structure and Palaeoclimate
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SAGES PhD Studentship Proposal
influenced by deep storm wave action, and receive low salinity surface waters from the
Minch, Slope Current and North Channel during tidal-induced down-welling [15]. This
environment changes over timescales of seasons to millennia as variations in the Gulf
Stream (and subsequent North Atlantic Drift) affect heat flux and source waters, storms
and wave intensities vary with the NAO [16], and surface waters are modified by regional
climate change and fluctuations in sea level [e.g. 5, 17].
By analysing dated coral fragments down through the core, we aim to recover short
subannual-resolution windows of palaeoceanographic information throughout the
Holocene. For this we will use facilities at SAMS (LA + solution ICP-MS/ICP-AES), at
SUERC (AMS and U-series dating) and Edinburgh University (ion microprobe). Records
will be integrated into oceanographic models to obtain a broader understanding of the
dynamics of the North Atlantic region.
Training Element
The student will receive a thorough training in sediment analysis, coral biogeography
+ structure, physical and chemical oceanography, and a full suite of palaeoreconstruction methodologies (stable isotopes, trace metals, radiometric dating). They
will be strongly encouraged to develop a detailed understanding of the oceanography
and climate change processes occurring in the North Atlantic, and to participate in
oceanic research cruises as opportunities arise. The student will have the opportunity to
take full advantage of expertise and equipment in all three of the institutions represented
(SAMS, BGS, University of Edinburgh).
Resources Required
Analytical instrumentation and methodologies are already in place within SAGES
institutions in Scotland, and with core samples now in hand, there is no need for
additional sampling trips to fulfil the objectives of the PhD project. This project will be
partially funded by the SAGES PhD studentship, with matching funds from a BGS BUFI
grant (application to be submitted October 31). We will be applying for an additional £3K
each year for analytical costs from SAGES Core Funds (application to follow). In
addition, we will bid for AMS dates and Ion Microprobe time through NERC. Further
details can be found in the financial statement at end of this proposal.
SAGES Tie-In and Collaborations
With this novel studentship proposal we honour the SAGES spirit of inter-institution
collaboration, bringing together the extensive coral analysis experience of D. Sinclair
(SAGES Lecturer at SAMS), with the Foraminifera and Holocene palaeoclimate
expertise of M. Elliot (SAGES, U of Edinburgh). The project crosses major discipline
boundaries, fusing geochemical oceanography with coral ecology (J. M. Roberts, SAMS)
and traditional sedimentary geology (D. Long, BGS).
The science we propose is central to SAGES Theme 3 (Oceans, Atmosphere and
Climate), and Theme 2 (Terrestrial Carbon Cycling). As specified for Theme 3: “A major
part of the research addresses the North Atlantic ocean currents and their importance in
the global climate system.” We address this in our quest to reconstruct Holocene
oceanography of the western Atlantic margin using sediment stratigraphy and
Foraminiferal and coral geochemistry. Theme 2 objectives are “to assess the balance
between carbon sources and sinks, quantifying volumes of greenhouse gases and
determining the processes affecting their release.” The oceans are a major, but poorly
understood C sink. By studying 14C ventilation, and organic carbon in the sediments, we
will quantify C fluxes between atmosphere, land and ocean.
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SAGES PhD Studentship Proposal
Figures
Figure 1: Location of BGS Vibra-Core sites on Mingulay Reef.
Figure 2: Ocean currents around northern Scotland (Modified from Turrell et al. 1996 [18])
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SAGES PhD Studentship Proposal
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