(More) Biogenic Barium and Organic Carbon Relationships on the Continental Margin: a Study From the Alboran Sea (Western Mediterranean)

The observed relationship between biogenic barium (bio-Ba) and organic carbon (Corg), and the relatively refractory nature of barite in non sulfate reducing sediments have led to the consideration of barite as a proxy for both modern and past biological processes. Beyond the uncertain phase partitioning between barite within total bio-Ba, recent studies have revealed that the relationship between bio-Ba and Corg fluxes in margin systems and open ocean systems differs markedly. In order to improve the knowledge of the behavior and significance of this component we present particulate bio-Ba fluxes obtained from three instrumented arrays with sediment traps moored in a continental margin area: the Alboran Sea (Western Mediterranean). The results obtained provide important insights into the influence of the oceanographic structures (upwelling off the Spanish coast, Western and Eastern Alboran Gyres), the intermittent fluvial discharge (southern Iberian Peninsula rivers) and the local bottom topography on the formation and transport of bio-Ba. Increased bio-Ba export efficiency at the end of enhanced productivity events suggest that the processes limiting bio-Ba formation in the area relate to the settling dynamics of particles. The ballasting effect of the abundant lithogenic and carbonate particles during massive aggregation processes during high productivity events may limit the decomposition of organic matter and enhance the transfer of particles rich in Corg and relatively poor in bio-Ba to the deep sea floor. We have also observed lateral transport of freshly sedimented material, including bio-Ba, from the continental slope to deeper areas. These results add to the growing caution in using bio-Ba as a productivity proxy in such highly dynamic environments.