Uptake, accumulation, and biotransformation of metal oxide nanoparticles by a marine suspension-feeder

A growing body of evidence indicates that some engineered nanoparticles (ENPs) are toxic to organisms that perform important ecosystem services in terrestrial and aquatic ecosystems. However, toxicity can be influenced by the biotransformation of contaminants, including ENPs, as it may alter the fate and transport of these substances. In turn, fate and transport can influence their bioavailability. To understand how biotransformation influences the fate and transport of ENPs in marine ecosystems, we exposed suspension-feeding mussels, Mytilus galloprovincialis, to two common nano-metal oxides, CeO(2) and ZnO, over a range of concentrations from 1mg L(-1) to 10mg L(-1), in a laboratory experiment. Mussels exposed to 10mg L(-1) accumulated 62μg g(-1) of Ce and 880μg g(-1) of Zn on a dry tissue basis but rejected 21,000μg g(-1) for Ce and 63,000μg g(-1) for Zn in pseudofeces. Scanning electron microscope evidence indicates CeO(2) remained as ENPs but ZnO did not after being rejected by the mussels. Mussels filtered most of the CeO(2) from the aqueous media, while a significant fraction of Zn remained in solution. Differences in ENP solubility affect ENP uptake, excretion, and accumulation in mussels. Our study highlights the potential role of marine suspension feeders in biotransformation of ENPs.