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Ocean life

Endangered oceans

Clearing an oil spillageClearing an oil spillage The Earth's oceans have been subjected to extensive pollution in recent years, endangering the lives of plants and animals—and quite possibly storing up harmful consequences for the planet as a whole. For example, when chemical waste from factories, including poisonous metals such as lead or mercury, is allowed to run into rivers or directly into the ocean, the harmful chemicals collect on the seabed, and are taken in by bottom-living animals such as shellfish. The chemicals then pass into the bodies of the animals that feed on them. For the predators at the top of the food chain, including humans, the effects can be deadly.


Ocean pollutionOcean pollutionThis illustration shows some of the ways in which the oceans can be polluted. Chemicals sprayed on to fields (1) run off into rivers, and then into the sea. Some factories discharge chemicals straight into the sea (2), through large pipes. Others take it out to sea and dump it there, sometimes in large containers that fall on to the sea bed (3). A leaking oil tanker (4) can pollute whole stretches of coastline, while fishing boats (5) discard nets that are hazardous to many kinds of wildlife. 

Algal bloom or Algal bloom or "red tide"Many of the waste products that pollute the oceans come from the land. Modern chemicals that are sprayed on to crops to kill pests often do not decay naturally. Rainwater washes them into rivers, from where they eventually flow down into the ocean. Chemical fertilizers spread over fields also flow from rivers into estuaries and coastal waters. They encourage the unnatural growth of some kinds of algae, which reduce the amount of oxygen in the water and kill off other life. Raw, untreated sewage from our homes has the same effect when it is pumped out into the ocean, or taken out to sea and dumped. It also contaminates shoreline sand or mud.

About 22 million tonnes of carbon dioxide from factories, cars and power stations are absorbed by the world’s oceans every day.

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