CHAPTER VI 



IMPACTS OF MARINE DEBRIS 



The tendency of marine mammals, seabirds, turtles, fish, and 

 invertebrates to become entangled in net fragments, packing 

 bands, and other synthetic materials lost and discarded at sea 

 has been recognized for many years. More recently, other 

 problems resulting from marine debris have become apparent. 

 These include ingestion of plastic bags and other plastic objects 

 by marine animals and the fouling of beaches, shorelines, and 

 coastal waters by all types of flotsam. Problems caused by 

 plastic debris exist throughout the world, but the situation is 

 particularly acute in certain ocean areas. For example, in the 

 North Pacific Ocean, debris-related injuries and mortality may 

 have contributed to declines in populations of North Pacific fur 

 seals, Hawaiian monk seals, Steller sea lions, harbor seals, and 

 a number of other marine species. 



Since the early 1980s, the Marine Mammal Commission has 

 played a major role in focusing domestic and international 

 attention on ways to assess and reduce the extent of the problem 

 for marine mammals and other species. Past efforts are discussed 

 in detail in previous Annual Reports. Activities undertaken by 

 the Commission and others during 1989 are discussed below. 



Background 



Since the early 1950s, plastics have become commonly used 

 for more and more purposes. Because most plastic products 

 degrade slowly and many are made for only one-time use (e.g. , 

 plastic bags and bottles) , they have contributed to an increase 

 in the amount of plastic debris accumulating in the marine 

 environment. Those items that float may be suspended at the sea 

 surface for extended periods of time, those that sink may remain 

 intact on the sea floor for years or even decades, and still 

 others may remain suspended at different depths in the water 

 column. 



As the amount of such debris increases, so too does its 

 threat to marine mammals, seabirds, turtles, fish, and 

 crustaceans. These organisms become entangled in loops and 

 openings of floating and submerged debris and they ingest items, 

 such as plastic bags and small plastic objects, that may resemble 

 natural prey. Animals that become entangled may drown, lose 

 their ability to catch food or avoid predators, or incur wounds 

 and infections from the abrasion of attached debris. Ingested 

 plastics may block digestive tracts, damage stomach linings, or 

 reduce feeding drives. 



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