Suspended particles are ubiquitously distributed in freshwater ecosystems and typically comprised of fine particulate matter with a diameter of less than 62 lm (Waters, 1995), although nanoparticles are generally defined as particulate matter with at least one dimension ranging between 1 and 100 nm (Moore, 2006). However, this is a somewhat arbitrary definition, and when applied to ecotoxicology, nanomaterials with a distribution of particle sizes around the nanoscale should also be considered, which may include some primary particles larger than 100 nm, or larger aggregates of nanoparticles of several hundred nanometers (Handy et al., 2008).