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Publication - Dr Joseph Stewart

    Extended calibration of cold-water coral Ba/Ca using multiple genera and co-located measurements of dissolved barium concentration

    Citation

    Spooner, PT, Robinson, L, Hemsing, F, Morris, PJ & Stewart, J, 2018, ‘Extended calibration of cold-water coral Ba/Ca using multiple genera and co-located measurements of dissolved barium concentration’. Chemical Geology, vol 499., pp. 100-110

    Abstract

    Biological productivity and ocean circulation are both important
    oceanographic variables that control the distribution of dissolved
    barium in the ocean interior ([Ba]sw). The ability to accurately reconstruct [Ba]sw
    will provide key constraints on these processes in the past. The
    geochemistry of cold-water corals has the potential to unlock
    paleoceanographic records at spatial and temporal resolutions not
    available using other sedimentary archives. Previous studies have
    suggested that the Ba/Ca ratio of coral skeletons is linearly related to
    [Ba]sw. However, these efforts have used a limited number of
    species, sparse global seawater databases, or have not explicitly
    measured the Ba/Ca ratio. Here we investigate the Ba/Ca ratio in a
    well-constrained set of cold-water scleractinian (aragonitic) corals as a
    proxy for [Ba]sw, using 58 specimens from 7 coral genera along with co-located measurements of [Ba]sw.
    We find that traditional chemical cleaning procedures do not
    significantly affect the Ba/Ca ratio of cold-water coral skeletons,
    allowing rapid sample throughput. We also determine that intra-sample
    variation in Ba/Ca ratios can be reduced by using larger sample sizes
    (e.g. 20 mg). By combining our results with existing data, we find that
    cold-water coral Ba/Ca is linearly related to [Ba]sw according to the relationship: Ba/Ca μmol/mol = [0.15 ± 0.02] [Basw nmol/kg] + [2.5 ± 1.4], (R2 = 0.7).
    We observe no species-specific ‘vital effects’ in cold-water coral
    Ba/Ca ratios, but site-specific effects could be a factor. Nevertheless,
    our results highlight the potential of Ba/Ca in cold-water corals to
    reconstruct biological and physical changes in the ocean interior.

    Full details in the University publications repository