Every year, huge quantities of waste and pollutants are dumped into the oceans. Ocean pollution, particularly in coastal waters, comes from activities on land and at sea. Fertilizers and pesticides used by farms, industrial and nuclear waste, exhaust gases emitted along the roads, used water and garbage are all dumped in waterways and end up in the ocean.
Atmospheric emissions from industry and transport are other significant sources of pollution from the land. Once emitted, many chemical compounds (copper, nickel, mercury, cadmium, lead, zinc and synthetic organic compounds) remain in the air for weeks, if not more. Carried by the wind, they often end up in the ocean.
Pollutants and garbage spread around the globe through ocean currents. Marine activities such as the extraction of fossil fuels, transports and fishing dump massive amounts of toxic substances in the ocean. Sound pollution, which profoundly affects the behaviour of some species—such as large marine mammals—is another increasingly serious problem.
Oil spills caused by boats colliding or running around is another significant international problem, now joined by similar spills of other dangerous, noxious substances.
Once in the marine environment, many pollutants from the land or the sea accumulate in the food chain and pose serious threat to ecosystems, whether along the coast or in deep waters.
According to a 2009 report from the United Nations Environmental Programme (UNEP), plastics—particularly bags and PET bottles—are the most common marine waste in the world. In many regional seas they make up over 80% of garbage. Plastic waste accumulates in land and marine environments around the world, decomposing very slowly into small toxic pieces which can be consumed by living organisms at all levels of the food chain. Many animals can mistake plastic for something edible. Sea turtles, in particular, confuse the floating bags for jellyfish, one of their favorite foods. A five-year study on fulmars in the North Sea region showed that 95% of the birds had plastic in their stomachs.
Every year, humans use billions of plastic bags (100 billion in the United States alone, according to the World Watch Institute). Only a small percentage is recycled, while the rest is used very briefly, usually just for a short shopping trip, then thrown out to fester in nature for thousands of years.