AUTHOR=Benaltabet Tal , Gutner-Hoch Eldad , Torfstein Adi 

TITLE=Heavy Metal, Rare Earth Element and Pb Isotope Dynamics in Mussels During a Depuration Experiment in the Gulf of Aqaba, Northern Red Sea

JOURNAL=Frontiers in Marine Science

VOLUME=Volume 8 - 2021

YEAR=2021

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2021.669329

DOI=10.3389/fmars.2021.669329

ISSN=2296-7745

ABSTRACT=Mussels are considered highly efficient marine biomonitors, tracing anthropogenic and natural variations in heavy metals and various organic compounds. While heavy metals depuration processes in biomonitors are of growing interest, less knowledge is available regarding their Pb isotopes and rare earth elements (REEs) accumulation-release dynamics, and their response to short-term anthropogenic and terrigenous perturbations. Here, we report the results of a relocation experiment where a group of mussels (Brachidontes pharaonis) were extracted from a contaminated lagoon in the Gulf of Aqaba, northern Red Sea, and placed in water tables that were flushed continuously with fresh, uncontaminated seawater. Pairs of mussels were removed periodically from the water table over a period of 13 weeks and trace and rare earth elements and Pb isotopic compositions were determined separately for mussel shells and soft tissue. The results display a clear decrease over time in the concentrations of various heavy metals and REEs in the soft tissue, in concert with a similar shift in the Pb isotopic compositions towards seawater values. By contrast, the elemental and isotopic composition of the shell presents little change over time.
Coupling between the Pb isotopic composition of corresponding soft tissue and shell samples allows back-calculation of the timing and magnitude of abrupt contamination events and provides quantitative constraints on long and short-term contamination events. Importantly however, considering the shallow coastal environment, the results may be biased by contributions of terrigenous material. Accordingly, Al-normalized element concentrations, Pb isotopes and the Ce anomalies, enabled the identification of two distinct terrigenous end members controlling the two sites. 
In summary, the study demonstrates the potential of using mussels as robust biomonitors of natural and anthropogenic environmental perturbations through the combination between elemental concentrations and the isotopic composition of Pb.