Click image to open full size
Microplastics in the Oceans
From Tire Dust to Plankton
Related Tools
Related Labs
Related Worksheets
Microplastics are tiny plastic particles smaller than 5 mm that are now found throughout the world’s oceans. They matter because their small size lets them mix with sand, float near the surface, sink into deep water, and enter living organisms. Many come from larger plastic trash breaking apart, but others come directly from tire dust, synthetic clothing fibers, and manufactured pellets. Once in the ocean, they are difficult to remove and can travel far from their original source.
In marine ecosystems, microplastics can be eaten by plankton, which are then eaten by small fish, larger fish, seabirds, and marine mammals. This movement through a food web can expose many organisms to plastic particles and the chemicals attached to them. Scientists have also found microplastics in human blood, lungs, and other tissues, showing that exposure can occur through food, water, and air. Reducing plastic waste at the source is one of the most effective ways to lower future ocean contamination.
Key Facts
- Microplastics are plastic particles with diameter d < 5 mm.
- Common sources include broken plastic waste, tire wear particles, synthetic clothing fibers, fishing gear, and industrial plastic pellets.
- Sunlight, waves, and abrasion fragment larger plastics into smaller pieces but do not make the plastic disappear.
- Bioaccumulation means particles or chemicals build up in an organism over time when intake is greater than removal.
- Biomagnification can increase the concentration of some pollutants up a food chain, especially when pollutants attach to plastics and are stored in tissues.
- Risk depends on exposure and hazard: Risk = exposure × hazard.
Vocabulary
- Microplastic
- A plastic particle smaller than 5 mm that can come from broken larger plastics or be released already small.
- Plankton
- Small drifting organisms in water that form the base of many ocean food webs.
- Bioaccumulation
- The buildup of a substance in an organism when it is taken in faster than it is removed.
- Food web
- A network of feeding relationships that shows how energy and matter move through an ecosystem.
- Synthetic fiber
- A human-made thread such as polyester or nylon that can shed tiny plastic fibers during use and washing.
Common Mistakes to Avoid
- Thinking all ocean microplastics come from bottles and bags is wrong because tire dust, textile fibers, fishing gear, and industrial pellets are also major sources.
- Assuming biodegradable means harmless in the ocean is wrong because many materials break down slowly in seawater and can still affect organisms before they fully degrade.
- Treating microplastics as only a surface-water problem is wrong because particles can sink, mix through the water column, enter sediments, and reach deep-sea habitats.
- Confusing bioaccumulation with biomagnification is wrong because bioaccumulation occurs within one organism over time, while biomagnification describes increasing concentration through higher levels of a food chain.
Practice Questions
- 1 A beach cleanup collects 12 kg of plastic fragments. If 0.8 percent of the mass eventually becomes microplastic particles, how many grams of microplastics could form?
- 2 A washing machine releases 700,000 synthetic fibers per load. If a household washes 5 loads per week, how many fibers are released in 4 weeks?
- 3 Explain how microplastics can move from a floating plastic bag to a human diet through an ocean food web, and identify one point where pollution could be reduced.