Plastic is the pollutant that refuses to go away. It does not dissolve, it does not rot, and it floats — so ocean currents can carry it thousands of kilometres from whoever dropped it. That combination is what makes it an ESS case study rather than just a litter problem.
📚 What you need to know
Plastic pollution is the build-up of plastic products in the environment, harming wildlife, habitats and people.
Wildlife is harmed four ways: ingestion, entanglement, transport of invasive species and chemical leaching.
Ocean gyres are huge circular current systems driven by winds and the Earth’s rotation. Floating plastic drifts into them and stays.
Microplastics are plastic pieces under 5 mm, either made that small or broken down from bigger items.
Microplastics enter food chains and, with the toxins stuck to them, become more concentrated at higher trophic levels — bioaccumulation within an organism, biomagnification up the chain.
Management works at three levels: reduce plastic use, capture it before it reaches the sea, and clean up what is already there.
How plastic gets from a bin to the middle of an ocean
Most marine plastic did not start at sea. It started on land, escaped into a drain or a river, and was carried downstream. Once it reaches open water, the currents take over.
Because gyres sit in international waters, no single country is responsible for the plastic that collects there — a classic tragedy of the commons.
Students often picture the Great Pacific Garbage Patch as a solid raft. It is not, and saying so in an exam signals you have only read a headline. Describe it as a diffuse concentration of fragments spread over a huge area.
How plastic harms wildlife
🧩 Four routes of harm
Ingestion. Animals mistake plastic for food. A floating bag looks like a jellyfish; a fragment looks like fish eggs. A stomach full of plastic gives a false feeling of fullness, so the animal starves even while it keeps eating.
Entanglement. Lost nets, packing straps and rings trap animals. Entangled seals and whales drown, get infected wounds, or cannot swim well enough to feed.
Moving species around. Floating plastic is a raft. Barnacles, algae and small crustaceans hitch a ride to coasts where they are not native and may outcompete local species.
Chemical leaching. Additives used to make plastics flexible or stable can leak out into the water, and some interfere with hormone systems and reproduction.
Why “ghost gear” is the worst kind: abandoned fishing nets are designed to catch animals, they are made from durable plastic, and nobody is coming back for them. They keep fishing for years after they are lost.
Microplastics and the food chain
Microplastics are pieces smaller than 5 mm. Some are made small on purpose — fibres shed by synthetic clothing in the wash, beads in some cosmetics. Most come from bigger plastic items being ground down by sunlight, waves and grit.
They matter because of their size. At under 5 mm they are exactly the size range that filter feeders and zooplankton mistake for food, which puts plastic at the bottom of the food chain rather than the top.
Plastic surfaces also attract oily, water-hating chemicals such as older industrial compounds and pesticides. So a swallowed fragment can deliver a concentrated dose of toxin along with the plastic itself.
Each predator eats many prey, and the toxin is not excreted as fast as it is taken in, so it stacks up. This is why top predators and people who eat them carry the highest loads.
Keep these two apart
Bioaccumulation = build-up inside one organism over its lifetime
Biomagnification = rising concentration up the trophic levels
Impacts on people and economies
Food safety. Microplastics have been found in fish and shellfish sold for eating, giving a direct route to humans.
Drinking water. Communities relying on polluted surface water get degraded water quality.
Tourism. Littered beaches drive visitors away, which hits hotels, restaurants and everyone whose income depends on them.
Fishing. Damaged gear, fouled propellers and lost catch all cost money.
Recreation. Swimming, diving and boating all become less pleasant or less safe.
What can actually be done
Level
Example strategy
Strength and weakness
Reduce at source
Bans on single-use items, deposit return schemes, taxes on plastic bags, redesign for reuse
Most effective long term because it stops the flow; needs political will and public support
Control the release
Better waste collection, river booms and traps, filters on washing machines, recycling infrastructure
Practical and fast to fit; does nothing about plastic already at sea
Clean up
Beach cleans, ocean collection systems, removal of lost fishing gear
Visible and good for awareness; expensive, slow, and can catch marine life too
EXAM PRACTICE
Evaluate the effectiveness of ocean clean-up projects as a strategy for managing plastic pollution. [4]
Give the strengths first
Removes plastic already in gyres, protects wildlife now, and raises public awareness which supports other policies.
Then the limitsIt treats the symptom, not the cause — plastic keeps arriving down rivers, so the problem returns.
Costly, works mostly on floating debris, and cannot recover microplastics or fragments that have already sunk. Nets may harm surface organisms.
Judge itUseful, but only as level 3. Real progress needs reduction at source“Evaluate” = strengths + weaknesses + a judgement. Missing the judgement costs a mark almost every time.
💡 Exam tip
Use the three-level management framework (reduce activity → control release → clean up) for any pollution question. It gives you an instant structure.
Quote the 5 mm definition for microplastics — it is a definite, markable fact.
When asked about gyres, mention wind patterns and the Earth’s rotation as the cause of the circulation.
Connect plastic to environmental value systems if the question invites it: an ecocentric view backs bans and reduction, a technocentric view backs clean-up technology.
Name a route to humans (seafood, drinking water) whenever a question mentions human health.
⚠️ Common mix-up
Saying plastic biodegrades. It fragments. The pieces get smaller but the polymer is still there.
Swapping bioaccumulation and biomagnification. One organism over time vs. one food chain going upwards.
Assuming all microplastics come from broken bottles. Synthetic clothing fibres in washing machine water are a major source.
Describing gyres as solid islands. They are dispersed, mostly small fragments.
Listing impacts without a mechanism. “Plastic kills turtles” scores little. “Turtles eat bags mistaken for jellyfish, blocking the gut” scores.
Up next: Testing and Monitoring Water Quality — how you turn “this river looks dirty” into numbers an examiner will accept.
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