Particulate biogenic, Ba, Sr and Ca and barite crystal contents from suspended matter were compared with acantharian water column distributions and individual Ba/Sr acantharian skeletal ratios during the European Iron Fertilization Experiment (EIFEX) in the Southern Ocean. In the upper 150 m, results indicate that the particulate biogenic Baxs signal is almost free of barite (BaSO4) particles and follows the same evolution as biomass parameters, implying that Ba is incorporated into or adsorbed onto biologically derived (biogenic) particles of which acantharians could account nearly the whole surface Baxs signal. In contrast, in the mesopelagic zone (150-1000 m), particulate biogenic Baxs is mainly composed of micro-crystalline barite. Calculations indicate that the combined acantharian associated Ba contents in the upper 150 m and between 150-500 m, if entirely transformed into barite, an unlikely condition, and dispersed in the 150-1000 m layer, could explain up to 20% of the mesopelagic Baxs contents. Our results thus indicate that acantharians are probably not the major source of particulate Ba-barite in the water column. They support the hypothesis that mesopelagic Baxs is mostly built-up as the result of biogeochemical processes within aggregates and its usefulness as a proxy of mesopelagic C remineralization. Copyright 2007 by the American Geophysical Union.