, 2004 and Cole et al., 2011). In other studies of marine debris, primarily from coastal assessments, 60–80% of marine debris is petroleum-based plastic (Derraik, 2002). Petroleum in any form entering the marine environment by anthropogenic means is a pollutant. A wide range of marine life, including marine mammals, reptiles and birds, is impacted by plastic pollution through entanglement or ingestion (Laist, 1987 and Van Franeker et al., 2011), and the persistent organic pollutants GABA receptor function that sorb onto plastic (Mato et al., 2001, Teuten et al., 2007, Teuten et al., 2009 and Rios et al., 2010). Plastic pollution also has the potential to transport non-native

species to other regions (Astudillo et al., 2009, Barnes and Fraser, Raf activity 2003, Bravo et al., 2011, Gregory, 2009 and Webb et al., 2009). The coastal margins of the South Pacific Ocean, and the Southern Ocean, are main contributors to plastic pollution in the SPSG (Lebreton et

al., 2012). In the western region of the SPSG plastic pollution is an emerging contaminant on island shorelines and adjacent coastal and oceanic waters, impacting fisheries, creating navigational hazards, and affecting tourism by its negative aesthetic appeal (Gregory, 1999a). In the southeastern South Pacific Ocean, surveys of plastic pollution near the coast, including fragments of foamed polystyrene, plastic bags, and food sacks from salmon farms identified aquaculture as the most significant contributor (Hinojosa and Thiel, 2009). Along the Chilean coast, large amounts of plastics also come directly from beach and shore activities (Thiel et al., old 2011). Other types of marine debris, including pumice and wood,

are injected into the ocean near Patagonian Fjords, with their abundance corresponding to river runoff after spring snowmelt (Hinojosa et al., 2011). Plastic pollution has also been detected in the surface waters of the Southern Ocean (Barnes and Milner, 2005). In a survey of waters near Antarctica, plastic pollution was the only type of marine debris found south of 63°S (Barnes et al., 2010). While large pieces of plastic pollution have been documented in the southern ocean and in the South Pacific, the presence and abundance of microplastics has not yet been confirmed. In particular, the area of the SPSG remains unstudied. Therefore, in this study we examined the abundance and composition of microplastics along a transect that crosses directly through the SPSG. To explore the presence and distribution of plastic pollution in the eastern South Pacific, an expedition on the sailing vessel Sea Dragon was organized and carried out by the 5 Gyres Institute. 8 The expedition started on March 23rd, 2011 from Valdivia, Chile and sailed to Pitcairn Island, which it reached on April 21, 2011.