Quantitative trace element micro analysis in calcite shell of the Great Scallop (Pecten maximus) by Laser Ablation ICP-MS: a daily archive of the biogeochemistry in temperate coastal environments

The development of Laser Ablation - Inductively Coupled Plasma - Mass spectrometry coupling (LA-ICP-MS) conduced to the quantitative micro analysis of trace elements (TE) in calcium carbonate (CaCO3) matrices by the use of CaCO3 standards (TE range of concentrations: 0-500 µg.g-1). Quantitative analyses of TE along the daily calcite striae of the Great Scallop shells (Pecten maximus) allowed the definition of chronological profiles at high temporal resolution. The significance of these profiles was then evaluated, particularly in the Bay of Brest (France). Background shell concentrations are directly related to TE dissolved concentration in the seawater surrounding the shell habitat and to the TE solubility constants within the carbonates, reflecting thus average environmental and hydroclimatic conditions. Recurrent transient or seasonal shell enrichments were observed for the molybdenum (Mo), the barium (Ba) and the manganese (Mn). Mo and Ba enrichments are identified as relevant tracers of phytoplankton dynamic in coastal temperate environments. Specific Mn enrichment, revealed for shells from the Bay of Seine, are related to continental inputs from the Seine river and to supplementary summer inputs induced by redox changes within the water column and at the sediment water/interface (SWI) in the estuary. The micro chemistry of trace elements in the shell can be thus considered as a relevant archive of environmental changes in coastal temperate ecosystems, and also allow to better constrain the biogeochemical cycle of trace elements at the sediment - water interface.