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Anthropogenic pollution reaches into the deepest regions of the ocean

Alan Jamieson/ Newcastle University Amphipods, which live at a depth of 10,000 meters, are showing elevated levels of pollutantsAlan Jamieson/ Newcastle University

Not even the depths of the oceans, which are regarded as the most untouched areas of the planet, are free from mankind’s influence. Researchers from the United Kingdom have identified elevated levels of organic pollutants, used for decades in industrial activities, in crustaceans caught in the deepest parts of the ocean. Using submersible traps, they collected samples of amphipods—crustaceans similar to shrimp—at depths ranging from 7,000 meters (m) to 10,000 m in two areas of the Pacific Ocean: the Mariana Trench in the North Pacific near the Philippines, and the Kermadec Trench in the South Pacific off New Zealand. These two abyssal zones extend for hundreds of kilometers and are among the deepest and least explored areas on Earth—the Mariana Trench at a depth of 10,994 meters and the Kermadec Trench at 10,047 m. When they analyzed the chemical composition of the amphipods, Alan Jamieson of England’s Newcastle University and his colleagues detected elevated levels of two chemicals: polychlorinated biphenyls (PCBs), which are fairly stable, toxic, low-flammability compounds used in refrigerants for decades; and polybrominated diphenyl ethers (PBDEs), used as a flame retardant in inks, fabrics and other materials by the automobile and aviation industries. Amphipods in the Mariana Trench showed higher concentrations of these environmental pollutants than did the ones from the Kermadec Trench, and in both cases the levels were higher than in those found in coastal areas regarded as clean (Nature Ecology and Evolution, February 13, 2017). PCB levels in the Mariana amphipods were 50 times higher than those found in crabs in the Liaohe River, one of China’s most polluted rivers. The data, says Jamieson, indicate that deep and surface waters are intimately connected.