Phd Thesis: Investigation of Shallow Marine Antarctic Environments Using the Annual Increment Growth Pattern of the Bivalve Mollusc Aequiyoldia Eightsii (Jay, 1839)
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PhD Thesis: Investigation of shallow marine Antarctic environments using the annual increment growth pattern of the bivalve mollusc Aequiyoldia eightsii (Jay, 1839). by Alejandro Román González 2017 Dedicated to Montserrat and Antonio i Thesis supervised by: Ian Hall1, James Scourse2, Lloyd Peck3, Paul Butler2, Caroline Lear1 and Martin Ziegler4 1 School of Earth and Ocean Sciences, Cardiff University, UK 2 School of Ocean Sciences, Bangor University, UK 3 British Antarctic Survey, UK 4 Earth Science Department, Utrecht University, NL ii Author’s declaration This work has not been submitted in substance for any other degree or award at this or any other university or place of learning, nor is being submitted concurrently in candidature for any degree or other award. Signature of Author …… Alejandro Román González… (candidate) Date …… 05/10/2018 Statement 1 This thesis is being submitted in partial fulfilment of the requirements for the degree of PhD. Signature of Author …… Alejandro Román González… (candidate) Date…… 05/10/2018 Statement 2 This thesis is the result of my own independent work and investigation, except where otherwise stated. Other sources are acknowledged by footnotes giving explicit references. A bibliography is appended. Signature of Author …… Alejandro Román González… (candidate) Date…… 05/10/2018 Statement 3 I hereby give consent for my thesis, if accepted, to be available online in the University’s Open Access repository and for inter-library loan, and for the title and summary to be made available to outside organizations. Signature of Author …… Alejandro Román González… (candidate) Date…… 05/10/2018 iii Title page Author’s declaration ………………………………………………………………… p. iii Index …………………………………………………………………………………………. p. iv Acknowledgements …………………………………………………………………… p. vii Note from the author ……………………………………………………………...… p. viii Summary ………………………………………………………………………………..… p. ix Chapter I: Introduction …………………………………………………………… p. 1 1.1 Area of interest …………………………………………………………….… p. 1 1.1.1 Oceanographic setting 1.1.2 Climate change in the Southern Ocean 1.1.3 Rothera Research Station, West Antarctic Peninsula setting 1.1.4 Signy Research Station, South Orkney Islands setting 1.1.5 Climatic modes 1.2 The Antarctic Aequiyoldia (Aequiyoldia eightsii, Jay 1839) …. p. 24 1.3 Sclerochronology ……………………………………………………………. p. 26 1.4 Rationale, aim and objectives …………………………………………... p. 27 Chapter II: Materials and Methods ………………………………………… p. 29 2.1 Site selection and description …………………………………….…… p. 29 2.2 Sample collection and curation ……………………………….……… p. 30 2.3 Laboratory processing …………………………………………..……… p. 31 2.3.1 Shell material 2.3.2 Sectioning and polishing 2.3.3 Etching and peel replica preparation 2.3.4 Imaging 2.3.5 Measuring 2.4 Investigation of shell growth ………………………………………..… p. 37 2.5 Crossdating ………………………………………………..………………… p. 40 2.6 Detrending and chronology construction ………………………… p. 41 2.7 Instrumental records ……………………………………………..……… p. 43 2.7.1 West Antarctic Peninsula records 2.7.2 South Orkney Islands records 2.8 Geochemistry ………………………………………………….…………… p. 47 iv Chapter III: Aequiyoldia eightsii shell growth …………………...…… p. 53 3.1 Morphometrics and specimen description ……………………..… p. 53 3.2 Ontogenetic growth trends ……………………………………..……… p. 57 3.3 Discussion …………………………………………….……………………… p. 64 Chapter IV: Instrumental records …………………………..……………… p. 71 4.1 Rothera time series instrumental record ……………………. p. 71 4.1.1 Seawater temperature 4.1.2 Salinity 4.1.3 Chlorophyll 4.1.4 Fast-ice 4.1.5 Geochemistry 4.1.6 Summary 4.2 South Orkney Islands records …………………………………... p. 89 4.3 Climatic indices ………………………………………………………. p. 96 4.3.1 Southern Annular Mode (SAM) 4.3.2 El Niño Southern Oscillation (ENSO) 4.4 Discussion ………………………………………………………………. p. 98 4.4.1 West Antarctic Peninsula 4.4.2 South Orkney Islands Chapter V: Shell geochemistry …………………………………………...…… p. 105 5.1 South Orkney Islands ……………………………………………….…… p. 107 5.1.1 High-resolution sampling 5.1.2 Low-resolution sampling 5.1.3 Comparison with instrumental records 5.2 West Antarctic Peninsula …………………………………………….… p. 121 5.2.1 High-resolution sampling 5.2.2 Low-resolution sampling 5.2.3 Comparison with instrumental records 5.3 Lateral isotopic fractionation ……………………………………….… p. 138 5.4 Discussion …………………………………………………………………..… p. 143 5.4.1 South Orkney Island 5.4.2 West Antarctic Peninsula 5.4.3 Stable isotope lateral fractionation 5.5 Appendix – Tables and figures ……………………………………….. p. 159 v Chapter VI: Sclerochronologies ……………………………………………… p. 166 6.1 West Antarctic Peninsula ……………………………………..……… p. 166 6.1.1 South Cove 6.1.2 Hangar Cove 6.1.3 Back Bay, Lagoon Island 6.1.4 Trolval Island 6.1.5 Comparison between master sclerochronologies 6.1.6 Comparison with instrumental records 6.2 South Orkney Islands …………………………………………..……… p. 188 6.2.1 1915 A. Bennett collection 6.2.2 1927 Discovery Investigations 6.2.3 1988 British Antarctic Survey collection 6.2.4 Comparison with instrumental records 6.3 Discussion ……………………….………………………………..………… p. 194 6.4 Appendix – Tables and figures ……………………………...……… p. 208 Chapter VII: Conclusions and final remarks ………………………… p. 212 7.1 Conclusions …………………………………………………………..…… p. 212 7.2 Limitations of the study ……………………….……………………… p. 214 7.2.1 Specimen collection 7.2.2 Study locations 7.2.3 Laboratory procedures 7.2.4 Aequiyoldia eightsii sclerochronologies 7.2.5 Geochemistry 7.3 Scope for future research …………….………………………………. p. 217 Reference list ……………………………………………………………………………. p. 221 Appendix – Published manuscripts …………………………………………. p. 251 vi Acknowledgements First I would like to thank the President’s Research Scholarship from Cardiff University which founded this PhD programme, providing the necessary funds to carry out the research presented here. I also want to express my gratitude to all the partner institutions for all their support and resources provided during this research. Especially I would like to thank all my supervisors (Ian Hall, James Scourse, Lloyd Peck, Paul Butler, Caroline Lear and Martin Ziegler), who provided support and intellectual inspiration throughout the entire length of the PhD programme. I would also like to give especial thanks to Dr. Alexandra Nederbragt from Cardiff University, who processed the minuscule geochemical samples for this study and whose technical expertise was invaluable. Carrying underwater work in Antarctica is challenging to say at least, I want to acknowledge the hard work and dedication of the British Antarctic Survey (BAS) divers who collected the specimens for this research. Furthermore, I would like to mention the support I have received from the ARAMACC Marie Curie Training Network partners for thinking of me during their training workshops, for that I am very thankful. I also want to thank the Natural History Museum, London, and especially the marine Mollusca curator Andreia Salvador, for lending some historical specimens, which have extended the original scope of this research project. In addition, I want to thank Mike Meredith and Hugh Venables (BAS) who provided me access to the Rothera Biological Times Series data, which was invaluable for understanding the local environmental processes in the coastal waters of Rothera Station. I am also grateful to the reviewers of this thesis for taking their time and attention to review it and whose comments help to improve the quality of the work presented here. My eternal gratitude goes to Carmen for the love and support that has granted me during the work in this thesis. Last but not least I want to thank my parents for their lifelong support and love they always have shown which knows no limits. Thank you Mum, thank you Dad. vii Note from the author Reference figures labelling – Figures in this thesis are label as Fig. 1.1, Fig 1.2, etc. The first number indicates the chapter number of the figure whereas the second number is the number of the figure within each chapter. When a figure is composed of two or more panels they are labelled using small print letters in abecedary order, e.g. Fig. 1.1a, Fig. 1.1b. Figures in the appendices are labelled using a capital A, e.g. Fig. A1.1, when an appendix figure has two of more panels, a small print letter is added, e.g. Fig. A1.1a, Fig. A1.1b, etc. General acronyms – Standard deviation (SD), standard error (SE), 95 % confidence intervals (CI0.05) and significance levels (SL). Published chapters – Part of the results presented in Chapter III: Aequiyoldia eightsii shell growth were published in Palaeogreography, Palaeoclimatology, Palaeoecology 465 (2017), 300-306 as: Román-González, A., Scourse, J.D., Butler, P.G., Reynolds, D.J., Richardson, C.A., Peck, L.S., Brey, T., Hall, I.R. Analysis of ontogenetic growth trends in two marine Antarctic bivalves Yoldia eightsi and Laternula elliptica : Implications for sclerochronology. Part of the results presented in Chapter VI: Sclerochronologies were published in The Holocene 27 (2017), 271-281 as: Román-González, A., Scourse, J.D., Richardson, C.A., Peck, L.S., Bentley, M.J., Butler, P.G. A sclerochronological archive for Antarctic coastal waters based on the marine bivalve Yoldia eightsi (Jay, 1839) from the South Orkney Islands. Pre-publishing versions of both manuscripts have been added at the end of this thesis in an appendix. viii Summary The research presented here constitutes the latest advances in the use of the Antarctic bivalve mollusc Aequiyoldia eightsii as a sclerochronological proxy for Antarctic coastal waters. A. eightsii has the potential to provide