Emerging Ocean Concern: Tiny Plastic Particles

Not necessarily. Just because they're degrading, doesn't mean they will "magically" disappear, as you're presuming. It takes thousands of years for larger plastics to break down into microplastics, that is, less than 5 micrometers in size. Known marine biogeochemical processes, including hydrolysis, photolysis, and microbially-mediated redox reactions, cannot break the polymeric backbone, leading to the extremely long persistence of plastic marine debris. This plastic reaches small organisms like plankton (the basis of the marine food web) and bio-accumulate over time in larger animals and eventually reach your food source when you eat fish.

In response to your comment on "it's time for new eco-worries," this is, in fact, a new field of research, because little is know about the effects of the bio-accumulation of microplastic in the marine environment.

H Jennings of WA 8:04PM June 15, 2010