The first result of an internet search for the term ‘high biodiversity’ is likely to be an image of a coral reef. The organisms that construct these reefs (hermatypic scleractinian corals) are threatened by environmental changes that include (1) episodically high seawater temperatures, (2) nutrient influx, (3) sediment influx, and (4) ocean acidification.
We can learn useful lessons about the likely effects of changing environmental conditions on modern reef corals by looking at how their ancestors responded to big environmental changes. The geological record of modern (scleractinian hermatypic) reef building corals goes back as far as the dinosaurs in the Mesozoic. Other reef-builders including tabulate and rugose corals are found in older Palaeozoic limestones. In many cases both the animal skeletons and the sediments that surrounded them when they were alive are preserved as limestone rock. By looking at the proportion of muds, sands and corals in these rocks through time, in combination with geochemistry (e.g. carbonate carbon isotopes and trace elements) and electron microscopy of the skeletons, we will be able to see, for example, how ancient reef-constructors including corals coped with influxes of mud and nutrients. Where preservation permits, carbonate oxygen isotopes in combination with sedimentology and electron microscopy will also enable us to look at effects of (locally or globally) changing seawater temperatures on ancient coral health and mortality.
One of the biggest changes to the Earth system in the last 500 million years was the origin and subsequent evolution of land plants with their roots and symbiotic mycorrhizal fungi. These newly evolved organisms were responsible for enhanced carbonate weathering (Brasier, 2011); establishment of the first meandering river systems, and for an increase in the amount of mud produced and stored on land (Davies and McMahon, 2018).
But if early Palaeozoic land plants were producing, trapping and binding voluminous amounts of mud on land then this raises questions about the effects that plant evolution may have had on coastal marine systems. First we ask whether there is geological evidence that the amount of mud, nutrients and organic carbon transported into shallow marine environments changed from the Ordovician onwards? Second, does the shallow marine carbon isotope record ever show the effects of these hypothesised changing volumes of terrestrially derived nutrient inputs to carbonate environments (thereby influencing organic carbon production and burial), either locally or globally? Third, have changes in the amount of mud and nutrients in coastal waters through time had any effects on the types of organisms (e.g. photoautotrophs vs heterotrophs) inhabiting shallow marine environments in proximity to coasts and rivers?
In this project the student will develop and test a hypothesis that from the Ordovician onwards early land plants dramatically reduced the export of mud and nutrients to shallow marine environments. The student will search for any trends in global and local shallow marine carbon isotope records, tied to volumes of terrigenous mud vs sand and/or limestone that may be deduced from examination of Earth’s sedimentary rock record. The student will similarly explore the rock record for changes in types and lifestyles of organisms that might have been related to variations in mud exported to shallow marine environments through the Phanerozoic.
The student will use a proven combination of field and laboratory studies to explore the ancient rock record, beginning with construction of a database from a literature search, and then using this to select appropriate field sites for further sedimentological, petrographic (advanced microscopy) and stable isotope geochemical investigations. Trends identified from this search will be verified using appropriate statistical and computer modelling techniques.
Field areas will be determined and prioritised based on database findings, but could include, for example, a selection from: Ordovician limestones of Ontario, Canada; Devonian, Carboniferous, Permian and Jurassic limestones of western mainland Europe and the UK; and Miocene limestones of the Mediterranean.
Applicants for this position should be interested in the evolution of life and environments through time, and enthusiastic about protecting and conserving Earth’s coral reefs. Individuals interested in palaeontology/palaeobiology and Earth surface environments would fit this project. A good undergraduate (BSc) degree in a subject such as geology, physical geography or environmental science, or potentially a relevant area of biology or chemistry, is required. An MSc would be desirable. Skills in isotope geochemistry, sedimentology, microscopy, and statistical modelling will be acquired during the project if the student does not have these already, but prior experience of one or more of these would be an advantage.
Supervisors on this project are Dr Alex Brasier (carbonate sedimentologist, and academic lead for the ACEMAC electron microscopy facility at the University of Aberdeen); Dr Neil Ogle (stable isotope geochemist, and laboratory manager of the Stable Isotope Facility at Queen’s University Belfast), and Dr Neil Davies (siliciclastic sedimentologist, University of Cambridge). This means that the project has access to all the required facilities, and the student will get regular (weekly) supervision, both in-person and via videoconferencing, from individuals who are global leaders in their fields.
Funding and eligibility information available here.
|Profile: Alex Brasier|
Institution: University of Aberdeen
Department/School: School of Geosciences
|Profile: Neil Ogle|
Institution: Queen's University, Belfast
Department/School: School of Natural and Built Environment
Dr Neil Davies, Lecturer in Sedimentary Geology, Cambridge University
Brasier, A. T. “Searching for travertines, calcretes and speleothems in deep time: Processes, appearances, predictions and the impact of plants.” Earth-Science Reviews 104.4 (2011): 213-239.
McMahon, William J., and Neil S. Davies. “Evolution of alluvial mudrock forced by early land plants.” Science 359.6379 (2018): 1022-1024.
Gattuso, J. P. et al., “Cross-chapter box on coral reefs.” Climate Change 2014: Impacts, Adaptation, and Vulnerability. Part A: Global and Sectoral Aspects. Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel of Climate Change. Cambridge University Press, 2014. 97-100.
Brasier, AT, Morris, JL & Hillier, RD 2014, ‘Carbon isotopic evidence for organic matter oxidation in soils of the Old Red Sandstone (Silurian to Devonian, South Wales, UK)’, Journal of the Geological Society , vol. 171, no. 5, pp. 621-634. DOI: HTTPS://DOI.ORG/10.1144/JGS2013-136
The student will use a proven combination of field and laboratory studies to explore the ancient rock record, beginning with construction of a database from a literature search, and then using this to select appropriate field sites for further sedimentological, petrographic (advanced microscopy, including using the ACEMAC electron microscope under the supervision of Dr Brasier) and stable isotope geochemical investigations (Î´13Ccarb and Î´ 13Corg, plus Î´ 18Ocarb in Belfast, under the supervision of Dr. Ogle). Trends identified from this search will be verified using appropriate statistical and computer modelling techniques (with Dr Davies in Cambridge).
Field areas will be determined and prioritised based on database findings, but could include, for example, a selection from: Ordovician limestones of Ontario, Canada; Devonian, Carboniferous, Permian and Jurassic limestones of western mainland Europe and the UK; and Miocene limestones of the Mediterranean. Here we could also make use of in-house expertise in 3d outcrop production and interpretation (Prof. John Howell, Aberdeen).
Expected Training Provision
The student will be trained in data collection and database construction; fieldwork, potentially including use of drones and 3d outcrop construction; advanced microscopy, including electron microscopy; stable isotope geochemistry; and statistical modelling. These are transferrable skills that can be widely applied in the environmental sciences. The student would also be trained in writing of reports and scientific articles, and in presentation skills.
Big changes to the bio- and geo-sphere resulted from colonisation of land environments from the Ordovician to Devonian, and whilst the impacts on terrestrial environments (e.g. changes in types of rivers, and carbon cycling in soils) have been looked at, the likely (inevitable?) impacts of e.g. changing fluxes of sediment and nutrients to shallow marine habitats and their organisms have not been closely considered. Hermatypic corals living in such environments are today vitally important for global biodiversity. It is entirely probable that trends hidden in the rock record will reveal how their ancestors faired under conditions of environmental change and stress. This is a novel approach that has serious potential for high-impact papers, and we hope might reveal interesting observations that contribute towards conservation of modern corals and their reefs.
Dr Brasier is a specialist in carbonate sedimentary rocks (limestones), their petrography (appearance under the microscope), and post-depositional alteration. He will supervise these aspects of the project.
Dr Ogle provides the necessary expertise in stable isotope geochemistry.
Dr Davies is a specialist in clastic sedimentary rocks (e.g. muds and sands) and will assist also with statistical modelling aspects. Regular (weekly) supervisory meetings will be held with the main supervisor, and at least monthly supervisory meetings with all 3 supervisors. These will be facilitated via MS Teams. The student will spend time in both Aberdeen (for data searching and microscopy) and Belfast (for isotope analysis and interpretation).
First six months: literature search and design and construction of database. Identification of field outcrops, and ideally at least one location in the UK visited early in the project (e.g. Jurassic of England, or Carboniferous rocks of Scotland).
6-18 months: continual addition to the database, plus additional fieldwork in at least 3 further field locations (UK, Europe, and/or Canada). Collection of field data, and sampling for stable isotopes.
18-24 months: Petrography including electron microscopy on samples, and sampling and analysis for stable isotopes. Presentation at a conference.
24-36 months: data analysis, including statistical modelling. Presentation at an international conference.
36 months-completion: writing of thesis and papers for publication.