Plastic ingestion by Procellariiformes in Southern Brazil

Abstract

The Procellariiformes are the birds most affected by plastic pollution. Plastic fragments and pellets were the most frequent items found in the digestive tract of eight species of Procellariiformes incidentally caught by longline fisheries as well as beached birds in Southern Brazil. Plastic objects were found in 62% of the petrels and 12% of the albatrosses. The Great shearwater, Manx shearwater, Cory’s shearwater and Antarctic fulmar were found to have greater quantities and frequencies of occurrence of plastic. There was no significant difference in the number of plastics between the birds from longline fisheries and beached birds. No correlation was found between the number of prey and number of plastics in the digestive tract of the birds analyzed, but this does not discard the hypothesis that, in some cases, the presence of plastic in the digestive tract has a negative effect on the feeding efficiency of these birds.

Introduction

Plastics are strong, light objects that can float on the ocean surface (Morris, 1980) and are often found in the stomach contents of a variety of albatrosses and petrels (Procellariiformes) (Huin and Croxall, 1996, Fry et al., 1987). Two classes of plastic are most found in Procellariiformes (Ryan, 1987): plastic pellets and fragments. Pellets are an intermediate stage in the manufacturing process of plastic (Colton et al., 1974), which are lost during manufacturing or transportation. These objects enter the marine ecosystem either directly or through drainage systems and are spread throughout the oceans on currents (Furness, 1983). Plastic fragments are small pieces broken off from larger items (fishing buoys, buckets and bottles), which are either discarded or lost at sea by fishing boats and other types of vessels (Merrell, 1980). Other ingested anthropogenic items include toys, polystyrene, monofilament lines, rubber and plastic tape (Robards et al., 1995).

In the Northern Atlantic, Procellariiformes are the birds that are most affected by the pollution of plastic particles (Moser and Lee, 1992), harmed through the digestion of these items due to the inability to regurgitate them (Furness, 1985b, Azzarello and Van Vleet, 1987). Plastic particles can remain in the ventriculus for months or even years before being completely eliminated (Furness, 1985a, Ryan, 1988).

Studies carried out on the extent of the effects of plastic ingestion by birds suggest that there may be a reduction in digestive capacity caused by the reduction in functional volume of the proventriculus and ventriculus, leading to a loss of energy reserves for migration and nidification (Connors and Smith, 1982, Furness, 1983, Furness, 1985b, Ryan, 1988). Other harmful effects are also cited, such as intestinal obstruction and ulcerations (Bourne, 1976, Bourne and Imber, 1982), blockage of gastric enzyme secretion (Azzarello and Van Vleet, 1987) and absorption of organochlorine adsorbed by the plastics (Carpenter et al., 1972, Ryan et al., 1988), which can cause reproductive failure and death (Azzarello and Van Vleet, 1987, Ryan et al., 1988, Lee et al., 2001).

Approximately 40 species of Procellariiformes from the Northern and Southern hemispheres use Brazilian waters as a feeding area during migration season (CBRO, 2006). Anthropogenic factors such as fisheries and marine pollution threaten these species, which are of great conservation interest due to the steep decline in their populations in recent decades (Croxall et al., 1998, Croxall and Gales, 1998, Ryan, 1998).

In the present study, we first evaluated the presence of plastics in the digestive tract of Procellariiformes incidentally caught by longline fisheries as well as beached birds in Southern Brazil. We then assess the differences in plastic ingestion between beached birds and birds killed by fisheries and test the hypothesis that the presence of plastic may lead to a decrease in food ingestion by seabirds.