Bioaccumulation and retention of lead in the mussel Mytilus galloprovincialis following uptake from seawater

Bioaccumulation of lead in the mussel Mytilus galloprovincialis from 210Pb-labeled bulk seawater (dissolved and particulate pathways combined) was examined over 21 days. The lead bioaccumulation factor (BAF) at equilibrium was estimated to be 211±10 ml g−1. This value was two orders of magnitude lower than BAFs reported in the literature for other trace metals in this bivalve indicating that lead is not efficiently accumulated by mussels from bulk seawater. The resultant lead distribution in mussels was 49±10% in soft tissues and 46±16% in the shell suggesting similar uptake rates (Bq day−1) in both compartments throughout the exposure. Total elimination for lead in mussels was adequately described by a short-term compartment with a biological half-life for loss of 1.4±0.3 days and a long-term compartment which released lead only very slowly (Tb1/2=2.5±0.7 months). No difference was noted for lead elimination rates in shell and in soft parts. When experimentally exposed to lead under conditions representative of natural environmental lead levels in water, including both that in the dissolved phase and in the food, the shell compartment was shown to contain the major fraction of the total lead accumulated by mussels. Therefore mussels may be considered as good bioindicators of lead contamination accumulated from the dissolved rather than from the particulate source. Furthermore, the relatively slow uptake and the long depuration half-life of lead will limit the ability of mussels to accurately record short-term variations in lead concentrations in the surrounding waters, a fact which should be taken into consideration in order to define the appropriate sampling frequency for mussels used in biomonitoring programs involving lead.