Bioaccumulation of copper (CuONPs vs ionic Copper) from sediments in the clam Scrobicularia plana

Sediments are considered a sink for metals, and nanoparticles transport in environmental is dominated by sedimentation. Consequently organisms that live in the sediments are more exposed to the risks related to exposure and toxicity of engineered nanoparticles (ENPs), especially deposit feeding invertebrates that have body surfaces in direct contacts with sediments and ingest huge amounts of sediment particles, due to the low source of food in sediments. In this study was carried out a 30-day experiment on juveniles of Scrobicularia plana exposed to spiked sediments with two different forms of copper, ionic (CuCl2) and nanoparticle (CuONP), both with low and high exposure. The first aim of this study was to evaluate bioaccumulation kinetics of the two different forms of copper in S. plana, in terms of bioaccumulation in the whole tissue and subcellular fractionation. The second aim was to evaluate the Condition Index of S. plana using the dry flesh weight: dry shell weight ratio condition index. Results of the bioaccumulation kinetics show a significant contamination and bioaccumulation of copper in whole animal tissue, that increased over time; for both copper forms, the organisms exposed to the highest concentrations showed the highest values of metal accumulation. The subcellular fraction results were in agreement with those of the bioaccumulated copper in the whole tissue. The results indicate the ability of the bivalve to detoxify bioaccumulated copper and that the concentration of copper associated to the metabolic available fraction (MAF) increases significantly as the concentration of Cu increases in the sediment. Thus, S. plana bioaccumulates copper, and has the ability to regulate the MAF rather than the total accumulated metal. Data on the Condition Index showed that the high CuCl2 treatment had a toxic effect on the physiological state of the organisms.