There's Toxic Pollutants In The World's Deepest Ocean Trenches

A new piece of research has looked at levels of pollutants found in tiny shrimp-like crustaceans in the Kermadec Trench near New Zealand and the Mariana Trench, the world’s deepest trench. At depths of 7,000 to 10,000 meters (23,000 to 32,800 feet,) this is thousands upon thousands of meters deeper than any other study looking at ocean pollution has ever delved.

Some of the findings from this new study, which has not been published yet, were revealed at a conference on deep ocean exploration in Shanghai, Nature News reports.

The study found significant levels of polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) in the crustaceans of both trenches. The research also found the animals from the Mariana Trench had noticeably high levels of PCBs – higher levels than you would find in the estuaries of China’s Pearl River and the Liao River, two of the most polluted rivers.

PBDEs are a “breed” of flame retardants used in many household appliances, vehicles, building materials, and textiles. PCBs are used to in the manufacturing of plastics and appliances, as well as to stop barnacles growing on ships' hulls. The notoriety of PCBs and PBDEs as a hazard to human and environmental health is well established. For example, PCBs have been banned in the US since 1979. However, despite that, the legacy of their widespread use before the ban still remains.

“The take-home message is that when you dump rubbish into the sea, it will ultimately sink. When [pollutants] fall into the trenches, they have nowhere else to go. So they’re just going to keep building up,” said Alan Jamieson, a deep-ocean researcher at the University of Aberdeen and an author of the study, according to Nature News.

What is most daunting about this research is that we know very little about deep oceanic trenches. An ongoing expedition by the National Oceanic and Atmospheric Administration’s (NOAA) Okeanos Explorer ship is currently delving into the Mariana Trench to study its biological inhabitants, along with hydrothermal vent sites, mud volcanoes, and seamounts. It’s a seemingly alien, untouched world down there – yet traces of human-made pollution can still be strongly felt.

[H/T: Nature News]