Voyage to the bottom of the sea: Tons of toxins are there

Crustaceans show vast contamination

Researchers exploring the ocean’s deepest reaches are accustomed to seeing oddities, from fish as fragile as tissue paper to translucent sea cucumbers. But even veteran deep- water scientists are shocked by the latest discovery at the very bottom of the sea: toxic pollution — lots of it.

Tiny shrimp- like crustaceans living in the Mariana Trench in the western Pacific, one of the world’s most remote habitats, are laced with staggering levels of industrial chemicals, a new study shows. Scientists found that some of the Mariana crustaceans are more contaminated with the harmful pollutants called PCBs than crabs living in waters fed by one of China’s most polluted rivers.

The scientists found high levels of flame retardants in the bodies of crustaceans living in the Kermadec Trench, the world’s fifthdeepest and more than 4,000 miles from the Mariana.

Humans have left a “footprint in the deepest places in the world,” said study co- author Alan Jamieson of Britain’s Newcastle University. “Not only are ( the pollutants) in every single sample, regardless of species, depth, trench, whatever, the concentrations are extraordinarily high. That was a big surprise.”

Anything that lives in in the Mariana Trench — the world’s deepest, at more than 6 miles — and other underwater gashes in the Earth’s surface is a tough customer. It must thrive in utter darkness and under pressures of 7 tons per square inch.

The scavengers called amphipods thrive by snatching any bit of food that floats by. But that voracity can backfire: The contaminants in the amphipods’ bodies probably came from the food they ate, the scientists write in this week’s Nature Ecology & Evolution.

It’s not clear whether the poisons do amphipods any harm, but ill effects would not be a surprise. Cancer and other health problems in animals have been linked to PCBs, and their manufacture was phased out decades ago.

Researchers did not trace the contaminants to their origins, but landfills are one possibility. Poorly maintained landfills could leach chemicals into rivers, which would funnel them to the ocean.

ALAN JAMIESON, NEWCASTLE UNIVERSITY Hirondellea gigas are voracious scavengers, known to consume almost any organic material that descends from the surface waters, including many pollutants.