On the barium-oxygen consumption relationship in the Mediterranean Sea: Implications for mesopelagic marine snow remineralization

Abstract

In the ocean, remineralization rate associated with sinking particles is a crucial variable. Since the 1990s, particulate biogenic barium (Baxs) has been used as an indicator of carbon remineralization by applying a transfer function relating Baxs 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 Baxs, prokaryotic heterotrophic production (PHP) and oxygen consumption (JO2- Opt; optodes measurement). We show that (1) higher Baxs (409 pM; 100 500 m) occurs in situations where integrated PHP (PHP100=500 D 0:90) is located deeper, (2) higher Baxs occurs with increasing JO2-Opt, and (3) there is similar magnitude between JO2-Opt (3.14 mmolm-2 d-1; 175 450 m) and JO2-Ba (4.59 mmolm-2 d-1; transfer function). Overall, Baxs, PHP and JO2 relationships follow trends observed earlier in the Southern Ocean. We conclude that such a transfer function could apply in the Mediterranean Sea.