LESSON 3
How Does Plastic End Up in the Ocean?
Introduction:
A Troubled Tide
Every second, a garbage truck’s worth of plastic enters the ocean. Oil spills, chemical run-off, sewage, heavy metals, ghost fishing gear—it all adds up.
Our ocean, once a symbol of vast, untouchable wilderness, is now under siege from human waste. Pollution is one of the most visible—and devastating—threats to marine life. But what exactly is polluting the sea, and how does it affect everything from whales to microscopic plankton?
In this lesson, we’ll break down the major types of ocean pollution and explore their impacts on ecosystems, climate, and even human health.
1. Plastic Pollution: A Global Crisis
Plastic doesn't disappear—it breaks into smaller fragments called microplastics, but it never fully biodegrades. Whether floating on the surface or sinking to the seafloor, it remains in the marine environment for centuries.
Sources of plastic pollution:
- Single-use plastics (bags, bottles, packaging)
- Lost or discarded fishing gear (ghost nets)
- Microplastics from synthetic clothing and personal care products
What are the impacts?
Ingestion and starvation
Animals like turtles and seabirds often mistake plastic for food. Consuming it blocks their digestive systems, causing internal injuries or starvation.
What are the impacts?
Entanglement and drowning
Nets, ropes, and plastic rings entangle whales, seals, and dolphins—leading to suffocation or loss of mobility.
What are the impacts?
Toxic exposure
Plastics absorb chemicals like PCBs and pesticides. When eaten by marine life, these toxins enter the food chain and accumulate in larger predators—including humans.
What are the impacts?
Food chain contamination
Microplastics are eaten by plankton and small fish, which are then eaten by larger fish, transferring plastic and toxins up the food web.
What are the impacts?
Habitat disruption
Floating plastics and ghost nets can smother coral reefs and seafloor habitats, making them uninhabitable.
Did you know?
The Great Pacific Garbage Patch is now estimated to be three times the size of France.
2. Chemical Pollution: The Hidden Toxins
Many pollutants aren’t visible—but their effects are deadly. Fertilizers, pesticides, oil, sewage, and industrial waste all flow from land into rivers, eventually reaching the sea.
What are the impacts?
Dead zones and oxygen loss
Fertilizer runoff fuels massive algal blooms. When algae die and decompose, they consume oxygen, leaving vast areas uninhabitable for marine life.
Bioaccumulation and poisoning
Heavy metals (like mercury and lead) and persistent organic pollutants (like PCBs) build up in fish tissue over time. These toxins are passed up the food chain, posing serious risks to wildlife and people who eat seafood.
What are the impacts?
Oil spill devastation
Oil smothers birds’ feathers and marine mammals’ fur, destroying their insulation. It also poisons fish, coral reefs, and shorelines—and recovery can take decades.
Did you know?
The Gulf of Mexico’s dead zone is larger than the U.S. state of Connecticut—caused by nutrient pollution from agriculture.
3. Noise and Light Pollution: Unnatural Oceans
We often overlook light and sound as pollutants, but in the underwater world, these invisible intrusions can be deeply disruptive.
What are the impacts?
Navigation and communication breakdown
Whales, dolphins, and many fish species rely on sound to navigate, find food, and communicate. Underwater noise from shipping, sonar, and drilling can drown out their calls, leaving them disoriented or separated from pods.
What are the impacts?
Stress and behavioural changes
Chronic noise causes stress responses in marine animals, affecting feeding, migration, and reproduction. Some species even flee once-important habitats.
What are the impacts?
Disrupted rhythms
Artificial lights along coastlines interfere with the biological cycles of many species. Sea turtles may avoid nesting or hatchlings may move inland, mistaking city lights for moonlight.
Did you know?
Some whales have been recorded changing their songs or diving patterns in response to ship noise.
Conclusion
We Pollute What We Depend On
Pollution is a problem we can see, feel, and fix. It doesn’t require advanced technology or billion-dollar budgets—just action, awareness, and commitment.
Every plastic item we refuse, every regulation we enforce, every clean up we support brings us closer to a cleaner, safer ocean.
Key Takeaways:
Plastic pollution is everywhere—from ghost nets to microplastics in plankton.
Chemicals from farming, industry, and oil spills create toxic, oxygen-deprived zones.
Noise and light pollution affect marine communication, reproduction, and survival.
Ocean pollution is a visible, solvable crisis we all have a part in ending.
NEXT LESSON
What Are “Dead Zones” and Why Do They Happen?
Next, we’ll explore oxygen-starved areas of the ocean—known as dead zones—how they form, why they’re growing, and what can be done to stop them.
START WITH THE BASICS
