Boron isotopes in diatoms; a proxy for pH?

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Author(s): Donald, Hannah K.; Foster, Gavin L.; Poulton, Alex J.; Moore, C. Mark; Swann, George E. A.; Hendry, Katharine R.
Author Affiliation(s): Primary:
University of Southampton, Southampton, United Kingdom
National Oceanography Centre Southampton, United Kingdom
University of Nottingham, United Kingdom
Cardiff University, United Kingdom
Volume Title: AGU 2016 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2016; American Geophysical Union 2016 fall meeting, San Francisco, CA, Dec. 12-16, 2016. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: High latitudes are important regions to consider in terms of ocean acidification, as they are climatically sensitive regions where the greenhouse gas CO2 is exchanged between the ocean and atmosphere. In theory, an improved understanding of these regions could be achieved using the boron isotope palaeo-pH proxy, in which CaCO3-based organisms including foraminifera are traditionally measured. The Southern Ocean is of particular interest in the global carbon cycle, however, foraminifera are scarce in sediments from this region. In contrast, siliceous diatoms are a dominant group of microfossils found within sediments, but as yet, the boron isotope-pH proxy has not been extended to opal. This is the major goal of the current study. Diatoms construct their frustules from biogenic silica by polymerising Si(OH)4, and boron content of these frustules, previously investigated by LA-ICP-MS (Mejia et al. 2013), is around 5-10 ppm. Here, current solution MC-ICP-MS methods used to measure boron isotopes in calcifying organisms have been adapted and developed for use with diatom opal. Preliminary results for sediment diatoms from the onset of major Northern Hemisphere glaciation will be presented (subarctic Northwest Pacific ODP site 882), as well as results for the cultured diatom species Thalassiosira weissflogii grown at varied pCO2. In light of these results, we will speculate on the nature of boron incorporation into diatom opal and its potential as an archive for palaeo-pH reconstructions.
Year of Publication: 2016
Research Program: ODP Ocean Drilling Program
Key Words: 07 Marine Geology and Oceanography; Boron; Calcium carbonate; Carbon; Carbon cycle; Carbon dioxide; Detroit Seamount; Emperor Seamounts; Foraminifera; Geochemical cycle; Leg 145; Microfossils; North Pacific; Northwest Pacific; ODP Site 882; Ocean Drilling Program; PH; Pacific Ocean; West Pacific
Coordinates: N502148 N502148 E1673600 E1673600
Record ID: 2017051608
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