Lucas, Zoe. 1992. Monitoring persistent litter in the marine environment on Sable Island, Nova Scotia. Marine Pollution Bulletin, 24(4): 192-199.
Summary (ZL): In this study, persistent litter included plastic, glass and metal items and materials that had been discarded, disposed of, or lost in the marine environment. These items would have entered the ocean via shipping, fishing and other marine activities; via mainland sources such as rivers, and sewage and storm water outlets; and as windblown litter, generally lighter items such as plastic packaging and balloons that can be carried by wind from inland areas to coastal environments.
One the earliest studies of persistent litter in the western North Atlantic was conducted on Sable Island. The island’s far offshore location makes it an ideal platform for monitoring events and trends in the marine environment. None of the human activities underway on the island are a significant source of debris on the beach, so virtually all the litter found on Sable has come from the ocean.
Beach surveys of persistent litter were carried out between May 1984 and September 1986. Six 500-m-long sampling sites were established on the north beach, chosen for similarity in shape, size and exposure, and located at roughly equal intervals along the beach. The sites were surveyed during summer and autumn, and all exposed and removable litter was collected. Large items, such as bundles of partially buried trawl net, were marked, recorded and left in place. Sites were not surveyed during December through April because travel and searches were restricted by narrow winter beach profiles, ice on the beach, and presence of grey seal breeding colonies. Each spring before the start of the study period, the sites were cleared of litter that had accumulated over winter.
Litter was sorted by material and size, and, when possible, by use or function. Data recorded included product type, manufacturer, country of origin, labelling language, and weight of plastics. Polyethylene sheet and bag fragments, plastic items and containers, and polypropylene rope and net fragments were weighed separately to the nearest 0.1 kg for each site.
A total 11,183 litter items were recorded, of which 92% were plastics. Plastic items collected ranged in size from large fish boxes to fragments as small as 5 mm. Given the observed seasonal and site consistency in accumulation rates, the survey data indicated that during summer and autumn, plastic litter had accumulated on the beach at a monthly rate of 202 items/km (by weight, ~8 kg/km). These values suggested an annual accumulation of >200,000 plastic items (8 metric tonnes) on the entire shoreline of Sable Island—north and south sides combined.
The amount of litter washing ashore on the island during the mid-1980s provided some appreciation of the scale of the problem in the ocean. Marine litter was then, and is now even more so, a threat to marine animals: seabirds, sea turtles, seals, whales and dolphins, fishes, and invertebrates. Individual animals eat or become entangled in debris afloat in the ocean, and this can become catastrophic at the population level when endangered species such as sea turtles or monk seals are affected.