Publication Date:
2017-08-19
Description:
Trace elemental ratios preserved in the calcitic skeleton of bamboo corals have been shown to serve as archives of past ocean conditions. The concentration of dissolved barium (Ba SW ), a bio-intermediate element, is linked to biogeochemical processes such as the cycling and export of nutrients. Recent work has calibrated bamboo coral Ba/Ca, a new Ba SW proxy, using corals spanning the oxygen minimum zone beneath the California Current System. However, it was previously unclear whether Ba/Ca bamboo coral records were internally reproducible. Here we investigate the accuracy of using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for Ba/Ca bamboo coral analyses and test the internal reproducibility of Ba/Ca among replicate radial transects in the calcite of nine bamboo corals collected from the Gulf of Alaska (643--720 m) and the California margin (870--2054 m). Data from replicate Ba/Ca transects were aligned using visible growth bands to account for non-concentric growth; smoothed data were reproducible within ~4% for eight corals (n = 3 radii/coral). This intra-coral reproducibility further validates using bamboo coral Ba/Ca for Ba SW reconstructions. Sections of the Ba/Ca records that were potentially influenced by non-carbonate bound Ba phases occurred in regions where elevated Mg/Ca or Pb/Ca and coincided with anomalous regions on photomicrographs. After removing these regions of the records, increased Ba/Ca bamboo coral variability was evident in corals between ~800--1500 m. These findings support additional proxy validation to understand Ba SW variability on interannual timescales, which could lead to new insights into deep sea biogeochemistry over the past several centuries.
Print ISSN:
0883-8305
Electronic ISSN:
1944-9186
Topics:
Geosciences
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