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Dr Joseph Stewart

Dr Joseph Stewart

Dr Joseph Stewart
PhD (Soton.), MESc (Oxon.)

Senior Research Associate

Area of research

Boron isotopes in deep sea corals

Office G43
Wills Memorial Building,
Queens Road, Clifton BS8 1RJ
(See a map)

+44 (0) 117 954 5247


I am an isotope geochemist studying the chemistry of marine biogenic carbonates to better understand the chemistry of the seawater in which these organisms lived.

My previous research has involved the taxonomic classification and geochemical measurement of ancient calcified plankton (foraminifera) recovered from deep ocean sediment cores to reconstruct ancient seawater temperatures (e.g. Mg/Ca) and changing patterns of continental weathering (e.g. Nd isotopes)

More recently research efforts have been focused on the refinement and application of boron isotope proxy for seawater pH measured in corals and calcified algae. The aims of this research are (i) to identify suitable coral substrates for use as pH biosensors, (ii) document changes in past ocean pH and (iii) to further our understanding of coral bio-mineralization and the impact of ocean acidification on marine califiers. 


2015 – 2017    Postdoctoral Researcher – National Institute of Standards & Technology, USA

  • Development of boron isotope pH-proxy in marine carbonates and application to NIST Environmental Specimen Bank samples
  • Production, bottling, and value certification of two new dissolved carbonate boron-isotope/trace-metal reference materials: NIST RM 8301c and NIST RM 8301f

2012 – 2015   Postdoctoral Research Fellow – Univ. of Southampton (NOCS), UK

  • The influence of seawater pH on the boron isotopic composition of deep sea corals
  • Advisor Prof Gavin Foster

2008 – 2012   PhD Geochemistry/Palaeoceanography – Univ. of Southampton (NOCS), UK  

  • Investigation into the effect of silicate weathering on climate across the Oligo-Miocene boundary
  • Supervisors Prof Rachael James and Prof Paul Wilson

2003 – 2007   MESc Earth Sciences (Geology) – Oxford University


2015 – 2017   Guest lecturer, College of Charleston, SC, USA

  • Regular guest lectures on IPCC and climate science to undergraduates


  • Coral
  • Foraminifera
  • Coralline Algae
  • Isotope geochemistry
  • Trace metals in carbonates



School of Earth Sciences

Earth Sciences staff

Research groups

Interdisciplinary groups

Recent publications

View complete publications list in the University of Bristol publications system

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