This study investigated sub-basin variability in dissolved (dBa)–excess particulate (Baxs) barium relationships and Ba flux patterns across the western and central Mediterranean Sea during late spring 2017 (PEACETIME cruise). The dBa concentrations increased from ~35 nmol L−1 near the surface to ~70 nmol L−1 at 2500 m, consistent with the relatively weak vertical dBa gradient typical of the Mediterranean. Depth profiles of dBa showed distributions consistent with Baxs dynamics associated with organic matter remineralization at mesopelagic depths (100–1000 m). Baxs exhibited basin-dependent maxima, with lower (<300 pM) depth-weighted average concentrations confined to the upper mesopelagic in the Tyrrhenian and Ionian basins and higher (up to 650 pM) and deeper concentrations (to ~1000 m) in the Algero–Provençal basin, suggesting contrasted remineralization horizon structures. A simplified steady-state 1-D approach yielded first-order mesopelagic dBa removal fluxes of ~0.3 ± 0.1 µmol m−2 d−1 in the Algero–Provençal basin to 1.7 ± 1.0 µmol m−2 d−1 in the Ionian basin, consistent with previous estimates obtained from a coupled dBa and parametric optimum multiparameter approach. Together, these paired dissolved and particulate Ba observations refined the Mediterranean Ba cycle framework and provided additional geochemical constraints for interpreting mesopelagic carbon remineralization processes.
Jacquet et al. (Mon,) studied this question.