Acantharians: a Missing Link in the Oceanic Biogeochemistry of Barium

Renate E Bernstein, Robert H Byrne, Johan Schijf

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Abstract

Inductively coupled plasma mass spectrometry was used to analyze the Ba and Sr concentrations of the celestite (SrSO 4 ) skeletons and cysts of individual acantharian specimens obtained from four diverse areas of the world’s oceans. Acantharian celestite Ba/Sr mole ratios ( χ Ba / χ Sr ) averaged 2.6×10 -3 with minimum and maximum values of 6.1×10 -4 and 2.5×10 -2 . Celestite Ba/Sr mole ratios were compared to dissolved Ba and Sr concentration ratios ([Ba 2+ ] T /[Sr 2+ ] T ) derived from GEOSECS stations that most closely corresponded to acantharian collection sites. Resultant Ba/Sr distribution coefficients ( D Ba/Sr =( χ Ba / χ Sr )/([Ba 2+ ] T /[Sr 2+ ] T )) in diverse areas of the world’s oceans are on the order of three or larger. These data, in conjunction with observations of acantharian mediated Sr 2+ depletions in the upper ocean, indicate that acantharians play a substantial role in the global oceanic Ba budget. Observation of Ba enrichments during celestite formation is consistent with expectations based on solidsolution–aqueous-solution precipitation dynamics and the much lower solubility of BaSO 4 compared to SrSO 4 . Furthermore, the small solubility product of RaSO 4 relative to SrSO 4 and BaSO 4 indicates that Ra should be enriched in both celestite and barite. Consequently, acantharians may have a substantial influence on the oceanic distributions of both Ba and Ra.

Original languageAmerican English
JournalDeep Sea Research Part I: Oceanographic Research Papers
Volume45
DOIs
StatePublished - Jan 1 1998

Disciplines

  • Life Sciences

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