Science & Technology in Action

13th Edition

Marine litter

BIM

Marine litter causes serious economic damage. The estimated cost across the EU for coastal and beach cleaning was almost €630 million per year, while the cost to the fishing industry is almost €60 million. Marine litter may be one of the fastest growing threats to the health of the world’s oceans.
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Lesson excerpt

The world’s lakes, seas and oceans have been, and are being affected by human activity. Only recently has it been realised that they are finite resources which are vulnerable to growing populations and industrialisation. Sewage discharge, agricultural runoff, toxic waste disposal, oil spillages and overfishing have all adversely affected marine ecosystems. Global warming is implicated in the destruction of coral reefs. Marine litter, also known as marine debris, refers to human-made solid waste that ends up in coastal and marine environments. It includes wood, fibres, paper, glass, metal and plastics. Objects most commonly discarded worldwide include cigarette butts (most common and not biodegradable!), plastic or paper bags, food wrappers/containers, eating utensils, plastic bottles, drink cans and straws, ropes. Plastics are generally not biodegradable.

Causes

About 80% of marine litter originates from land. People discard litter, deliberately or accidentally, which is carried to the sea by wind or rivers. Rain washes litter off streets into drains. Poorly-maintained waste disposal facilities, rubbish bins and refuse trucks fail to contain the litter which often finds its way to the sea. Ships can lose cargoes and fishing boats can lose nets and equipment by accident or in storms. Tsunamis and hurricanes result in millions of tonnes of marine debris. Warfare and economic collapse generate sunken or abandoned ships, planes and weapons.

Effects

At an immediate level, litter fouls any environment and lowers its aesthetic value. This affects life quality and can also be a health hazard as litter attracts vermin. Litter at sea has fouled ship propellers and interfered with water intake. Ships abandoned in waterways can affect currents and increase shading – this can alter the ecosystem. As they disintegrate, metals, oil and toxic materials enter the water. Conversely, ships and rigs can be deliberately sunk to create artificial reefs. Much litter sinks in the ocean where it interferes with coral reefs and can cause injury to animals. The effects on benthic organisms have not yet been properly determined. Nets entrap birds, fish and seals. Ingested plastics have blocked animals’ tracts leading directly to suffocation and starvation. Large quantities of ingested plastics have given animals a feeling of being full so they cease eating. More subtly, chemicals from plastic have mimicked the effect of hormones such as estradiol, possibly disrupting the physiology of animals. Wood, paper and plastics are often coated with polish or preservatives which are released into the water.

True or False?

  1. World demand for plastics is greater than its current ability to recycle or safely dispose of it. true
  2. Plastic microbeads are never used in hygienic products or cosmetics. false
  3. Cigarette tips are readily biodegradable. false
  4. Most litter in the world is found at sea. false
  5. Litter generated in the middle of a continent is no threat to marine life. false
  6. Some sea litter has proved to be of archaeological interest. true
  7. Sea turtles have apparently been known to mistake plastic bags for jellyfish prey. true
  8. Suspensions of plastic microparticles can reduce the light reaching aquatic plants. true
  9. Objects containing rubber, glass or metal are rarely biodegraded completely. true
  10. Dealing with sea litter involves legal, cultural and financial challenges. true

Glossary of terms

absorption
a process by which a liquid of gas enters the bulk of a material
adsorption
a process by which a liquid of gas adheres to the surface of a material
benthic
relating to the sea floor
biodegradable
can be broken down into simple substances by decomposers such as fungi and bacteria
biodegradable plastics
plastics that naturally disintegrate over time
circular economy
an economy in which all materials are recycled
estradiol
an estrogen; the primary female sex hormone
marine debris
pieces of rubbish or detritus found in the marine environment
marine litter
litter that is found in the sea
microplankton
micro-organisms found in plankton
microplastics
plastic particles that are generally smaller than 1 mm; sometimes added (as microbeads) to cosmetics etc.
PCB
printed circuit board; a nonconducting board which holds electronic components that are linked by conductive tracks
plastics
polymers; materials that can be easily moulded
skimmer boats
a boat used to gather marine litter
suspension
a mixture in which fine particles are suspended in a fluid where they are supported by buoyancy