NOT far off the coast of Guam lies the deepest point on Earth's surface, the Mariana trench. Its floor is 10,994 metres below sea level. If Mount Everest were flipped upside down into it, there would still be more than 2km of clear water between the mountain's base and the top of the ocean. Such isolation has led many to assume that it and similar seabed trenches will be among the few remaining pristine places on the planet. However, a study led by Alan Jamieson of Newcastle University, in England, has shown that nothing could be further from the truth. As Dr Jamieson and his colleagues report this week in Na- ture Ecology and Evolution, trenches are actually loaded with pollutants.
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