Plastic in the Ocean
Marine debris are found in all sea areas of the world – not only in densely populated regions, but also in remote places far away from any obvious sources. Marine litter originates from many sea-based and land-based sources and causes a wide spectrum of environmental, economic, safety, health and cultural impacts. The very slow rate of degradation of most marine litter items, mainly plastics, together with the continuously growing quantity of the litter and debris disposed, is leading to a gradual, but dramatic increase in the quantities of marine litter in our oceans and world shores.
The majority of marine debris is composed by or originated from plastic litter, such as plastic bags and containers, bottle caps, lost or abandonned fishing nets and lines, styrofoam or small plastic pellets.
Where does it come from?
Though 20% comes from ocean sources like derelict fishing gear or ocean dumping, 80% comes from land-based activities, through wind-blown landifll waste, for example.
Impacts on marine life
Lost and discarded fishing gear is a primary cause for environmental, economic and public safety concern, but plastics are far the most pervasive of marine litter items. Plastic in water appears as food to animals such as sea birds, marine turtles and cetaceans and their ingestion can cause intestinal blockage, malnutrition and poisoning. One study found that 82 of 144 bird species examined contained small debris in their stomachs, and in many species the incidence of ingestion exceeds 80% of the individuals). On the other hand, animals can be caught, entangled and hurt by such debries which can lead to health problems or even death.
What is the dimension of the problem?
Estimates for the rate of litter accumulation in the world’s seas and oceans vary substantially. The highest estimates suggest accumulation rates as high as 7 billion tonnes per annum . The plastic dominates the marine debris not only due to its intensive production and extensive use in the last decades but also because it is not biodegradable. Therefore, it can remain in the oceans for a long time and travel long distances through marine currents, accumulating along the shores or converging ocean zones. A conspicuous example of the latter is found in the central North Pacific Ocean, known as the Pacific trash vortex, where the pieces of plastic outweigh surface plankton by a factor of 6 to 1 .
United Nations Environment Programme: http://www.unep.org/regionalseas/marinelitter/
- UNEP/IOC Guidelines on survey and monitoring of marine litter, 2009.
- Moore, C., Moore, S., Leecaster, M. & Weisberg, S., 2001. A comparison of plastic and plankton in the North Pacific central gyre. Marine Pollution Bulletin 42, 1297–1300.
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