What do we learn about the Mariana Trench? PASSAGE The Mariana Trench(马里亚纳海沟) in the northern Pacific is the deepest part of the world's oceans. You might think a place that remote would be untouched by human activity. At its deepest the water in the trench is near freezing and the pressure would crush a human like a bug. But it is polluted. Scientists have only recently explored it. Among them is biologist Alan Jamieson of Newcastle University in England. His team dropped what they call a mechanical "lander" down into the trench. It had cameras and water samplers and some baited traps. When the lander surfaced, the traps contained amphipods(片脚类动物) -- shrimp like crustaceans (甲壳动物).The amphipods were contaminated with toxic chemicals used for decades in industry, as well as other industrial pollutants known as persistent organic pollutants. "Every sample we had," Jamieson says, "had contaminants in it at very high or extraordinarily high levels." How high? He compared the contamination level in his Mariana amphipods to crabs living in waters fed by one of the most polluted rivers, as well as amphipods from other parts of the world. He says, "And what we were finding in the deepest place in the world were (levels) hugely higher, 50 times in some cases." He thinks the pollutants might get to the trenches by holding on to plastic that's floating in the ocean. Fish and other marine animals absorb pollutants as well. Eventually, the plastic and the dead animals fall to the bottom. Like dirt in your house, a lot of it will collect at the lowest points. It's simply a matter of gravity. Marine biologist Katherine Dafforn at the University of New South Wales in Australia says the discovery of such high levels of toxic chemicals in these trenches is "disturbing". She says, "A lot of chemicals will have far-reaching impacts that we don't necessarily know about." And those impacts might be in places that people don't pay much attention. Jamieson says just because pollution is out of sight doesn't mean it's harmless. "We've got to remember, planet Earth is mostly deep sea, and to think that it's OK just to ignore it is a little bit irresponsible."