Plastic debris at the micro-, and potentially also the nano-scale, are widespread in the environment.
Microplastics have accumulated in oceans and sediments worldwide in recent years, with maximum
concentrations reaching 100 000 particles m3. Due to their small size, microplastics may be ingested by
low trophic fauna, with uncertain consequences for the health of the organism. This review focuses on
marine invertebrates and their susceptibility to the physical impacts of microplastic uptake. Some of the
main points discussed are (1) an evaluation of the factors contributing to the bioavailability of microplastics
including size and density; (2) an assessment of the relative susceptibility of different feeding
guilds; (3) an overview of the factors most likely to influence the physical impacts of microplastics such
as accumulation and translocation; and (4) the trophic transfer of microplastics. These findings are
important in guiding future marine litter research and management strategies.