Plastics and seabirds

Plastic Kills Seabirds

Plastic debris is an increasing source of global pollution, especially in the marine environment. Plastic polymers are made from petroleum and do not biodegrade but break down into smaller and smaller pieces, increasing their surface area and potential for interaction with the environment. Plastics comprise 80% of marine debris and being less dense than water many pieces float at or near the surface. This impacts on marine wildlife through ingestion, entanglement and potential chemical affects. Ingestion of plastic bags may lead to positive buoyancy impeding the ability of marine vertebrates and seabirds to dive for food. More than 270 marine species including zooplankton ingest plastic, with microplastics (< 5mm) of particular concern as they may transfer up the food chain. About half of all seabird species are known to ingest plastic and as seabirds live much of their lives at sea or in remote locations, the number of deaths and injuries attributed to plastic ingestion or entanglement is difficult to determine. In August 2003 the Australian government listed 'injury and fatality to vertebrate marine life caused by ingestion of, or entanglement in, harmful marine debris' as a key threatening process by under the Environmental Protection and Biodiversity Conservation Act 1999 (EPBC Act)1.

The CSIRO's three-year marine debris project (2011 - 2014) involved the survey of Australian coastal marine debris at sites approximately every 100 km along the coastline2. Three-quarters of rubbish washed ashore is plastic and mostly from Australian sources, with the main items being cigarette products and plastic bags. In offshore Australian waters the density of plastic varies but is very high being up to 40,000 pieces per square kilometre near major population centres2. This also points to a local source for the pollution. There is strong evidence that in South Australia where there is a container deposit scheme less plastic beverage containers are lost to the environment2.

The breeding success of the Lord Howe Island Flesh-footed Shearwater Puffinus carneipes population is in rapid decline due to starvation of the chicks3. The island is their largest breeding site in Australia and the species is classified as vulnerable in New South Wales. When the migratory adult shearwaters arrive at Lord Howe in September to breed no plastic is found in their stomachs but a few months later, after foraging in the Tasman Sea, plastic is found in their stomachs. This is fed to their chicks that tend not to regurgitate until nearly fledged, so plastics accumulate in their stomach during the nestling period4. In 2012 Ian Hutton flushed the stomachs of fifty chicks and every chick had some plastic, many with such large amounts that they would die of starvation9. In the 2011 survey, one dead bird had 274 pieces of plastic comprising 15% of its body weight10. Besides starvation some birds die of mechanical injury from pieces of plastic perforating their gastrointestinal tract.

Marine plastic also acts as a sponge and concentrates heavy metals and other toxins such as organic pollutants (polychlorinated biphenyls) on its surface at more that 1000x the surrounding seawater. When ingested the adsorbed contaminants on the plastic enter the bloodstream and are incorporated into the tissues with the potential to harm the animal and cause death. Fish that ingested marine plastic showed signs of stress in their livers5. Seabirds accumulate these contaminants in their feathers enabling sampling to be non-destructive. The breast feathers of breeding adult Fleshy-footed Shearwaters on Lord Howe Island are contaminated with extremely high levels of mercury with evidence suggesting the source is contaminated plastic6. Further investigation to determine the percentage from other sources is required.

The global use and production of plastic is accelerating around the world. With its permanence in the environment, marine plastic is a growing environmental issue. An increasing number of marine fauna are being affected and the CSIRO predicts that 95% of seabird species will be ingesting plastic by 20502. The management of anthropogenic debris before it reaches the ocean should be a priority for this generation with waste management infrastructure developed in countries where there are no formal systems in place7. A greater responsibility to reduce waste through recycling and reuse also needs to be adopted7, not only to reduce litter and landfill, but also to reduce the environmental damage done by manufacturing with raw materials, the source of which may be unsustainable8.

  3. in shearwaters.pdf

    For ABC programs on Plastic Oceans (CSIRO) and the Flesh-footed Shearwaters


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Revised March 2015