The biological production of marine suspended barite and the barium cycle in the Western Mediterranean Sea

Suspended particulate barium was measured in the Western Mediterranean along 4 profiles sampled during the PHYCEMED 1 cruise in 1981. The non-terrigenous fraction of particulate barium (i.e. excess Ba; Ba_xs) can account for up to 96% of total barium. This fraction follows the barite settling and dissolution rate model we described earlier for the Atlantic Ocean, confirming barite as the carrier of excess barium. We propose that these Ba_xs concentrations, which are higher in the Western Mediterranean than in the overall Atlantic, may represent an adaptation of the microplankton to the high densities and density gradients of surface Mediterranean waters.A mass-balance for Ba in the Mediterranean Sea shows: (1) that the atmospheric source must be much more important than previously reported: (2) that contrary to the Atlantic situation, the internal recycling of barium is of little importance compared to the flow of barium through the system.