Seabirds indicate changes in the composition of plastic litter in the Atlantic and south-western Indian Oceans Peter G. Ryan * Percy FitzPatrick Institute, DST/NRF Centre of Excellence, University of Cape Town, Rondebosch 7701, South Africa article info Keywords: Plastic ingestion Seabirds Virgin pellets Tristan da Cunha South Africa Atlantic Ocean Western Indian Ocean abstract I compare plastic ingested by five species of seabirds sampled in the 1980s and again in 1999–2006. The numbers of ingested plastic particles have not changed significantly, but the proportion of virgin pellets has decreased 44–79% in all five species: great shearwater Puffinus gravis, white-chinned petrel Procellaria aequinoctialis, broad-billed prion Pachyptila vittata, white-faced storm petrel Pelagodroma marina and white-bellied storm petrel Fregetta grallaria. The populations sampled range widely in the South Atlantic and western Indian Oceans. The most marked reduction occurred in great shearwaters, where the average number of pellets per bird decreased from 10.5 to 1.6. This species migrates between the South and North Atlantic each year. Similar decreases in virgin pellets have been recorded in short-tailed shearwaters Puffinus tenuirostris in the Pacific Ocean and northern fulmars Fulmarus glacialis in the North Sea. More data are needed on the relationship between plastic loads in seabirds and the density of plastic at sea in their foraging areas, but the consistent decrease in pellets in birds suggests there has been a global change in the composition of small plastic debris at sea over the last two decades. Ó 2008 Elsevier Ltd. All rights reserved. 1. Introduction Floating plastic litter is one of the most widespread and abun- dant marine pollutants (Coe and Rogers, 1997; Derraik, 2002). It is eaten by a wide range of marine organisms, including seabirds, marine mammals, turtles and fish (Laist, 1997), reducing effective stomach volume (Ryan, 1988a), introducing toxic chemicals (Ryan et al., 1988; Mato et al., 2001) and, in severe cases, blocking the digestive tract (Fry et al., 1987; Derraik, 2002). Surface and shal- low-diving seabirds are especially prone to eating plastic debris, with petrels and storm petrels accumulating large loads in their stomachs due to their inability to pass them through the pyloric sphincter into the intestine (Furness, 1985). The size of plastic arti- cles ingested is related to bird size; larger birds eat larger items (Furness, 1985; Ryan, 1987). Initial studies of plastic ingestion found that most plastics ingested by small and medium-sized sea- birds were virgin, industrial plastic pellets (Day et al., 1985; Ryan, 1987; Laist, 1997). These small beads, 1–5 mm across, are the pri- mary feedstock of the plastics industry. Spilled pellets are carried in waste water, accumulating at sea where they are long lived and disperse far from source areas (Gregory and Ryan, 1997). First reported in prions Pachyptila spp. in New Zealand in 1960 (Harper and Fowler, 1987), pellets were reported in large numbers at sea off eastern North America in the early 1970s (Carpenter and Smith, 1972; Colton et al., 1974), and are now ubiquitous throughout the world’s oceans (e.g. Robards et al., 1997; Moore et al., 2001). In the early 1990s, the plastics industry established education programmes (e.g. Operation Clean Sweep, see www.opclean- sweep.org) to prevent the loss of pellets. There are few data to demonstrate the efficacy of this initiative. Semi-quantitative sur- veys in New Zealand and islands in Oceania suggest that the num- bers of pellets on beaches decreased in the early 1990s (Gregory and Ryan, 1997). Short-tailed shearwaters Puffinus tenuirostris sampled in the North Pacific in the late 1990s contained similar plastic loads to those sampled in the late 1970s, but the proportion of virgin pellets had decreased from 55–73% to 33% (Vlietstra and Parga, 2002). More recently, a long term decrease has been re- corded in the mass of virgin pellets in northern fulmars Fulmarus glacialis stranded on Dutch beaches over the last 20 years (van Franeker et al., 2005). In this study, I report decreases in the num- bers of virgin pellets in five species of seabirds that range widely in the Atlantic and south-west Indian Oceans, and discuss whether this indicates that there has been a decrease in the numbers of pel- lets at sea. 2. Methods I obtained ingested plastics from seabirds either by dissecting dead birds to examine their stomach contents (Ryan, 1987), or by finding plastics in regurgitations of Subantarctic skuas Catharacta antarctica roosting at Inaccessible Island, Tristan da Cunha, central 0025-326X/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.marpolbul.2008.05.004 * Tel.: +27 21 650 2966; fax: +27 21 650 3295. E-mail address: peter.ryan@uct.ac.za. Marine Pollution Bulletin 56 (2008) 1406–1409 Contents lists available at ScienceDirect Marine Pollution Bulletin journal homepage: www.elsevier.com/locate/marpolbul