Debris size and buoyancy influence the dispersal distance of stranded litter

• Published in: Marine pollution bulletin 2016-09, Vol.110 (1), p.371-377
• Main Authors: Fazey, Francesca M.C., Ryan, Peter G.
• Format: Article
• Language: English
• Subjects: Atlantic Ocean; Bathing Beaches; Biofouling; Brackish; Dispersal; Environmental Monitoring - methods; Flotation; Marine; Marine debris; Microplastics; Plastics - analysis; Size; South Africa; South Atlantic; surveys; Waste Products - analysis; Water Pollutants, Chemical - analysis; water pollution
• ISSN: 0025-326X; 1879-3363
• DOI: 10.1016/j.marpolbul.2016.06.039

Recent at sea surveys of floating macro-debris in the southeast Atlantic Ocean found that debris increases in size with distance from shore, suggesting that many smaller items, which dominate litter close to urban source areas, sink before dispersing far into the ocean. We test whether this pattern is evident in beach litter in the same region. Freshly stranded beach litter was collected at increasing distances (0km, 100km, 200km and 2800km) from Cape Town, a major urban litter source. Mean size and buoyancy of litter items increased significantly with distance from Cape Town. Size-specific sedimentation due to the ballasting effect of biofouling is a plausible explanation for the disappearance of smaller, less buoyant items. Our results provide further evidence that many low buoyancy items sink and support the hypothesis that size and buoyancy are strong predictors of dispersal distance for floating debris. •Beach litter size and buoyancy increases with increased distance from pollution sources.•This reflects trends found in floating litter in the same region (southeast Atlantic Ocean).•The effect was evident over a distance of 200km.•Our results suggest that many smaller plastic items fail to disperse long distances.•Size-specific sedimentation due to biofouling is a plausible explanation for these trends.