In a study published last week in the journal Nature, scientists discovered extremely high levels of toxic chemicals (PCBs and related compounds) down 10 km deep in the Marianas and Kermadec Trenches. The trenches, which could easily swallow the entirety of Mt. Everest, were originally thought to be one of the last pristine habitats left on Earth. However, pollutants have settled via ocean dispersal and vertical transport in the deepest reaches of the world’s oceans, only to then be taken up (or bioaccumulated) by the creatures that dwell there.
“Small crustaceans that live in the pitch-black waters of the trench, captured by a robotic submarine, were contaminated with 50 times more toxic chemicals than crabs that survive in heavily polluted rivers in China.”
PCBs, although banned in the 1970s, have made their way up the food chain and showed elevated levels in all samples that were taken from both trenches.
“We still think of the deep ocean as being this remote and pristine realm, safe from human impact, but our research shows that, sadly, this could not be further from the truth,” said Alan Jamieson of Newcastle University in the UK, who led the research.
“We still know more about the surface of the moon than that of the ocean floor,” said Katherine Dafforn at the University of New South Wales in Australia. She said the new research showed that the deep ocean trenches are not as isolated as people imagine. “Jamieson’s team has provided clear evidence that the deep ocean, rather than being remote, is highly connected to surface waters. Their findings are crucial for future monitoring and management of these unique environments.”