To cite this version:Julien Thébault, Laurent Chauvaud. Li/Ca enrichments in great scallop shells (Pecten maximus) and their relationship with phytoplankton blooms. Palaeogeography, Palaeoclimatology, Palaeoecology, Elsevier, 2012, 373, pp.108-122. <10.1016/j.palaeo.2011
AbstractPhytoplankton dynamics in coastal oceans is a major component of the global biogeochemical carbon cycle, and is currently affected by global change through modifications in levels of primary productivity and composition of phytoplankton communities. Despite many attempts, no straightforward geochemical proxy has been found yet in marine biogenic carbonates for reconstruction of past phytoplankton dynamics with high temporal resolution. Here, we report on subweekly variations of lithium-to-calcium ratios (Li/Ca shell ) along the axis of maximum growth of great scallop shells ( Comparison of these results with shell growth measurements (increment width) and environmental parameters suggests (i) that shell calcification rate is likely the main factor controlling incorporation of Li in Pecten maximus shell calcite, (ii) that seawater temperature has only a weak positive influence on Li/Ca shell of this species over the range 8-18°C, and (iii) that during diatom blooms, additional amounts of Li may be trapped in the shell following dissolution of Li-rich frustules of edible species in the digestive tract of scallops, being responsible for Li/Ca shell peaks. Therefore, we suggest that Li/Ca shell ratio may be a novel proxy for timing and magnitude of diatom blooms in coastal ecosystems. Analysis of ancient shells may thus provide useful information on past phytoplankton dynamics and on the importance of recent shifts observed from diatoms to non-siliceous phytoplankton in coastal areas affected by anthropogenic activities.