Microstructure and biomineralization of barnacles: implication as sentinel tool for heavy metal detection at Lake Timsah, Egypt

Abstract This study investigates the use of two common barnacle species, Amphibalanus amphitrite and Amphibalanus eburneus as sentinel organisms for metal pollution at Lake Timsah, Egypt. XRD and FTIR were used to assess biomineralization progress of shell at different ages. The study confirmed the high capability of barnacles to accumulate metals with relation to its parietal structure and shell crystalline construction. Metal concentrations in barnacles, sediment, and seawater followed the order Fe > Al > Pb > Cd where barnacles indicated higher metal accumulation. The bioaccumulation of metals tended to be higher in soft tissues than shells and it was species- and size-dependent. The mineral composition of the shells showed that calcite crystal size increases, while macrostrain decreases, with age. The calcite crystals of A. eburneus exhibited smaller crystallites and higher macrostrains compared to A. amphitrite due to higher rates of metal deposition. The parietal/basal plate configuration in small barnacles contributed significantly to high metal accumulation in their body. For more precise future environmental assessment regulations, the youngest animals of A. eburneus were promising sentinel organisms for monitoring Cd, Al, and Fe metals, while small barnacles of A. amphitrite are potential for monitoring Pb.