On the barium-oxygen consumption relationship in the Mediterranean Sea: implications for mesopelagic marine snow remineralisation

Abstract. In the ocean, remineralisation rate associated with sinking particles is a crucial variable. Since the 90's, particulate biogenic barium (Ba_xs) has been used as an indicator of carbon remineralization by applying a transfer function relating Ba_xs to O₂ consumption (Dehairs's transfer function, Southern Ocean-based). Here, we tested its validity in the Mediterranean Sea (ANTARES / EMSO-LO) for the first time by investigating connections between Ba_xs, prokaryotic heterotrophic production (PHP) and oxygen consumption (JO₂-Opt; optodes measurement). We show that: (1) higher Ba_xs (409 pM; 100–500 m) in situations where integrated PHP (PHP100/500 = 0.90) is located deeper, (2) higher Ba_xs with increasing JO₂-Opt, and (3) similar magnitude between JO₂-Opt (3.14 mmol m⁻² d⁻¹; 175–450 m) and JO₂-Ba (4.59 mmol m⁻² d⁻¹; transfer function). Overall, Ba_xs, PHP and JO₂ relationships follow trends observed in the Southern Ocean. We believe that such transfer function could apply in the Mediterranean Sea with no restriction.