Barium uptake into the shells of the common mussel (Mytilus edulis) and the potential for estuarine paleo-chemistry reconstruction

In this study we test if calcite shells of the common mussel, Mytilus edulis, contain barium in proportion to the water in which they grew. Similar to all bivalves analyzed to date, the [Ba/Ca](shell) profiles are characterized by a relatively flat background [Ba/Ca](shell), interrupted by sharp [Ba/Ca](shell) peaks. Previous studies have focused on these [Ba/Ca](shell) peaks, but not on the background [Ba/Ca](shell). We show that in both laboratory and field experiments, there is a direct relationship between the background [Ba/Ca](shell) and [Ba/Ca](water) in M. edulis shells. The laboratory and field data provided background Ba/Ca partition coefficients (D-Ba) Of 0.10 +/- 0.02 and 0.071 +/- 0.001, respectively. This range is slightly higher than the D-Ba previously determined for inorganic calcite, and slightly lower than foraminiferal calcite. These data suggest that M. edulis shells can be used as an indicator of [Ba/Ca](water), and therefore, fossil or archaeological M. edulis shells could be used to extend knowledge of estuarine dissolved Ba throughputs back in time. Moreover, considering the inverse relationship between [Ba/Ca](water) and salinity, background [Ba/Ca](shell) data Could be used as an estuary specific indicator of salinity. The cause of the [Ba/Ca](shell) peaks is more confusing, both the laboratory and field experiments indicate that they cannot be used as a direct proxy of [Ba/Ca](water) or phytoplankton production, but may possibly be caused by barite ingestion. (c) 2005 Elsevier Inc. All rights reserved.