Coupling shell growth and geochemistry in giant clams to explore biomineralization pathways

Project Background
Bivalves belonging to the subfamily Tridacnidae (the so-called ‘giant clams’) play an important ecological role in tropical reef environments, providing food and shelter to a wide variety of organisms, contributing to the reef framework, and counteracting eutrophication. Their shells are also considered valuable tropical sclerochronological archives due to their rapid shell accretion (mm/yr to cm/yr), dense shell structure, and longevity (>100 yrs). Previous work has showcased the use of isotopic and geochemical tracers in Tridacna shells to explore highly time-resolved changes in reef environments. Despite their considerable use as a bioarchive and their importance in the reef structure, there is limited knowledge on the biomineralization of their shells. This project aims to understand the key environmental factors (e.g. light, temperature and nutrient availability) that control shell growth and microstructures in these important marine calcifiers and look at the potential of Tridacna shells from different environments for generating biogeochemical proxy records.

Project Aims and Methods
This PhD looks to use an interdisciplinary approach to explore the fundamental controls of Tridacna shell growth and biomineralization by examining several shell specimens from diverse reef environments in Sabah. Reefs from Sabah are part of the Coral Triangle, the region with the highest marine biodiversity on Earth. Under the current global change scenario, it has been hypothesized that turbid reefs maybe more resilient to bleaching events, therefore they may act as refugia habitats that could potentially support the conservation of clear-water reefs in the long term. Besides coral biodiversity studies, it is fundamental to incorporate other key reefal taxa, such as giant clams, to better understand environmental responses of biota to temperature and light controls. This approach will use advancing imaging and mineralogical techniques such as Scanning Electron Microscopy (SEM), Confocal Laser Scanning Microscopy (CLSM), and Electron Backscatter Diffraction (EBSD) to examine shell growth, microstructure and mineralization pathways of giant clams from turbid and clear water environments in Borneo. Alongside this, the student will use isotope ratio mass spectrometry and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) analysis on recently living Tridacna shells to generate geochemical proxy records (d18O, Sr/Ca, , Ba/Ca) to reconstruct environmental changes in both turbid and clear-water environments. These reconstructions will aid in deciphering how environmental stressors impact marine sessile organism and their ability to calcify. In addition to exploring the modern shell collection,you will also utilize the fossil collection to determine if similar biomineralization features persisted under different environmental conditions.

Candidate Requirements
The project would suit a candidate interested in the application of mineralogy analysis to explore changes in calcification and giant clam microstructures or growth features. You should be interested in the development of paleoclimate and environmental proxies in giant clam shells in reef environments in the tropics.

CASE or Collaborative Partner
The student will conduct several visits per year to the Natural History Museum, interacting with their co-supervisors and curators. They will have access to critical expertise on the giant clams and reef evolution along with facilities for species identification and description. The student will also engage with the public through outreach events at the NHM.

Training
You would gain experience in advanced imaging and mineralogical analysis focusing on via light microscope and state-of–the-art SEM, CLSM, and EBSD techniques and sclerochronological processing techniques. You will also receive training on generating stable isotope and trace elemental analyses using micro sampling techniques including a micromill and conventional carbonate stable isotope mass spectrometry and LA-ICP-MS. The broad range of training involved in this project should equip the student with the tools and experience needed to explore a career in palaeoclimate reconstruction, with a focus on tropical environments, and indeed many aspects of marine conservation.

How to apply:

You should apply to the Doctor of Philosophy in Earth and Ocean Sciences with a start date of October 2020.
Please refer to another project for further details on how to apply. Or contact us.

If you wish to apply for more than one project please email [Email Address Removed].

The deadline for applications is 16:00 on 6 January 2020.

Shortlisting for interview will be conducted by 31 January 2020.

Shortlisted candidates will then be invited to an institutional interview. Interviews will be held in Cardiff University between 10 February and 21 February 2020