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Boron isotopes as a proxy for pH in siliceous and calcareous marine algae

Boron isotopes as a proxy for pH in siliceous and calcareous marine algae
Boron isotopes as a proxy for pH in siliceous and calcareous marine algae
Rising CO2 in the atmosphere has directly led to a reduction in surface ocean pH -a process known as ocean acidification. There is a need to understand past climates in terms of ocean pH change in order to be able to relate these to the current effects of climate change on marine organisms. One way of doing this is by measuring boron isotopes in marine carbonates, such as foraminifera and corals, to estimate past ocean pH, and thus to infer past pCO2. Key regions of atmospheric-ocean CO2 exchange are the Southern Ocean and subarctic North Pacific, and they are also areas where modern ocean acidification is occurring fastest. The current application of the boron isotope proxy is restricted in these high latitude regions due to lack of calcareous organisms preserved in the sediment here. Therefore, there is a need to expand the boron isotope proxy into novel materials, such as diatoms and coralline algae, which are found in these key high latitude habitats in abundance.
This thesis aims to investigate whether the hard parts of marine algae (siliceous: di-atoms; calcareous: coralline algae) are suitable archives for the boron isotope pH proxy. This is achieved by examining: (i) which boron species could be incorporated into the frustule/skeleton; (ii) the relationship between boron isotopic composition and seawater pH, and hence the sensitivity of boron isotopes in each organism to changes in seawater pH; (iii) the palaeo-archive potential of each organism. These aims are addressed by developing a method to measure boron isotopes and boron content of diatoms by MC-ICP-MS, calibrating the boron-pH relationships in a species of diatom using culturing experiments, applying this calibration to sedimentary diatoms collected from a core in the subarctic North Pacific, and also by investigating the relationship between boron isotopes and seawater pH in a species of coralline algae.
University of Southampton
Donald, Hannah, Katie
574e955f-ec6a-49e1-b86a-8bf7d1ab877c
Donald, Hannah, Katie
574e955f-ec6a-49e1-b86a-8bf7d1ab877c
Foster, Gavin
fbaa7255-7267-4443-a55e-e2a791213022

Donald, Hannah, Katie (2017) Boron isotopes as a proxy for pH in siliceous and calcareous marine algae. University of Southampton, Doctoral Thesis, 178pp.

Record type: Thesis (Doctoral)

Abstract

Rising CO2 in the atmosphere has directly led to a reduction in surface ocean pH -a process known as ocean acidification. There is a need to understand past climates in terms of ocean pH change in order to be able to relate these to the current effects of climate change on marine organisms. One way of doing this is by measuring boron isotopes in marine carbonates, such as foraminifera and corals, to estimate past ocean pH, and thus to infer past pCO2. Key regions of atmospheric-ocean CO2 exchange are the Southern Ocean and subarctic North Pacific, and they are also areas where modern ocean acidification is occurring fastest. The current application of the boron isotope proxy is restricted in these high latitude regions due to lack of calcareous organisms preserved in the sediment here. Therefore, there is a need to expand the boron isotope proxy into novel materials, such as diatoms and coralline algae, which are found in these key high latitude habitats in abundance.
This thesis aims to investigate whether the hard parts of marine algae (siliceous: di-atoms; calcareous: coralline algae) are suitable archives for the boron isotope pH proxy. This is achieved by examining: (i) which boron species could be incorporated into the frustule/skeleton; (ii) the relationship between boron isotopic composition and seawater pH, and hence the sensitivity of boron isotopes in each organism to changes in seawater pH; (iii) the palaeo-archive potential of each organism. These aims are addressed by developing a method to measure boron isotopes and boron content of diatoms by MC-ICP-MS, calibrating the boron-pH relationships in a species of diatom using culturing experiments, applying this calibration to sedimentary diatoms collected from a core in the subarctic North Pacific, and also by investigating the relationship between boron isotopes and seawater pH in a species of coralline algae.

Text
Donald, Hannah_PhD_Thesis_Nov_17 - Author's Original
Restricted to Repository staff only until 20 November 2020.
Available under License University of Southampton Thesis Licence.

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Published date: 20 November 2017

Identifiers

Local EPrints ID: 416836
URI: http://eprints.soton.ac.uk/id/eprint/416836
PURE UUID: 75841627-6525-4bc4-86a3-9ed26505a5de
ORCID for Gavin Foster: ORCID iD orcid.org/0000-0003-3688-9668

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Date deposited: 11 Jan 2018 17:30
Last modified: 07 Jun 2019 00:32

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Contributors

Author: Hannah, Katie Donald
Thesis advisor: Gavin Foster ORCID iD

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