Trophic Transfer of Nanoparticles in a Simplified Food Web
Richard D. Holbrook, Karen E. Murphy, Jayne B. Morrow, Kenneth D. Cole
Nanotechnological innovations depend largely on the unique chemical and physical properties of engineered nanomaterials. However, the same properties that make engineered nanomaterials attractive for numerous applications also contribute to their unexpected behavior in environmental and biological systems. Potential environmental risks posed by engineered nanomaterials, which include bioaccumulation and biomagnification by aquatic organisms, has been a central argument for regulating the growth in the nanotechnology sector. Here we show that surface-functionalized nanoparticles (carboxylated and biotinylated quantum dots (QDs)) are readily accumulated by ciliated protozoan via endocytosis, but not by bacterial ingestion, and can be transferred to higher trophic organisms such as rotifers in a simplified predator-prey food web. QD surface chemistry influenced the kinetic bioaccumulation pattern and depuration rates of the ciliates but had little influence on bioaccumulation factors. Neither type of QD was found to be bioaccumulative nor biomagnifiable using traditional risk assessment protocols and definitions. Lack of biomagnification in rotifers is attributed to high QD depuration rates. These results indicate that engineered nanomaterials can undergo trophic transfer by aquatic organisms and that the potential for nanomaterial biomagnification is largely governed by the depuration rate.