Every year, huge quantities of waste and pollutants are dumped into the oceans. Many of these substances did not even exist 50 years ago. Ocean pollution, particularly in coastal waters, comes from activities on land and at sea. These pollutants are then spread around the planet by ocean currents.
Over 300 million tons of plastic are produced globally each year. About 8 million tons of plastic waste end up in the ocean, mostly via rivers, but also from plastic tossed overboard from ships. Much of this plastic waste is carried over great distances by oceanic currents and gathers in huge vortices. On this journey—which lasts about 10 years—large pieces of plastic are progressively eroded and eventually broken down into particles smaller than 5 millimeters in diameter, or microplastics, which are eaten by sealife and consequently by us (find out more: Slow Food International Congress Chengdu Motion 6: Plastic in the Planet’s Ecosystem).
Fertilizers and pesticides from farms, industrial and nuclear waste, dirty water, and garbage are all dumped in waterways and end up in the ocean.
Emissions from industry and transport are another significant source of pollution from the land. Chemical compounds like copper, nickel, mercury, cadmium, lead, zinc, and synthetic organic compounds remain in the air for weeks, if not more. They are then carried by the wind and often end up in the ocean.
Sound pollution, which profoundly disturbs the behavior of some animal species such as large marine mammals, is another increasingly serious problem.
Oil spills caused by boats colliding or running aground are a significant international problem with a long history, and now similar spills of other dangerous, noxious substances are worsening the situation.
Once in the marine environment, many pollutants from the land or the sea accumulate in the food chain and pose a serious threat to ecosystems, whether along the coast or in deep waters.