, 2006 and Thompson et al., 2004). Marine observational surveys allow divers or observers on Enzalutamide nmr boats and in submersibles to record the size, type and location of visible plastic debris. While this technique is effective at detecting macroplastics over relatively large areas, microplastics will often go undetected, and – as debris is not collected – the litter can undergo no further assessment (Pruter, 1987 and Ryan et al., 2009). Furthermore, the subjective nature of observational work leaves such censuses open to bias (Ryan

et al., 2009). Finally, biological sampling involves examining plastic fragments consumed by marine biota. A number of marine organisms can mistake plastic debris for prey (Blight and Burger, 1997, Tourinho et al., 2010 and van Franeker et al., 2011). By dissecting beached marine animals, or by instigating regurgitation in some seabirds, their gut contents can be analysed for the presence of plastics, which can then be identified and quantified

(van Franeker, 2010). The Fulmar has routinely been used to assess the abundance of plastic debris at sea for some time and the abundance of microplastics within the stomachs of Fulmars has now become one of the ecological quality assessment markers used by OSPAR to assess the abundance of plastic debris at sea (van Franeker et al., 2011). Whilst migration and movement of this ocean PFKL foraging seabird precludes matching their plastic load with specific locales, regional differences and trends over time have become see more apparent (Blight and Burger, 1997, Tourinho et al., 2010 and van Franeker, 2010). Plastic litter has permeated marine ecosystems across the globe (Derraik, 2002, Lozano and Mouat, 2009 and Ryan et al., 2009). Driven by ocean currents, winds, river outflow and drift (Barnes et al., 2009, Martinez et al., 2009 and Ng and Obbard, 2006) plastic debris can be transported vast distances to remote, otherwise pristine, locations, including mid-ocean islands (Ivar do Sul et al., 2009), the poles

(Barnes et al., 2010) and the ocean depths (Lozano and Mouat, 2009). However, whilst plastic litter may be found throughout the marine environment, the distribution of this debris is heterogeneous (Martinez et al., 2009 and Moore, 2008). In this section we discuss how microplastics accumulate along coastlines and within mid-ocean gyres, examine the variable position of microplastics within the water column and consider microplastic abundance over time. Coastlines receive plastic litter from both terrestrial and marine sources, terrestrial sources of litter will typically dominate close to urban areas, sites of tourism and near river outflows, whilst marine debris will be deposited along shorelines when caught in near-shore currents (Ryan et al., 2009). Using sediment analysis, Thompson et al.