When you think of ocean pollution, plastic rings and bottles probably come to mind, but the problem goes much deeper than that—literally. According to Nature World News, deep-sea researcher Alan Jamieson and a team from the University of Aberdeen recently shared findings from two 2014 expeditions into two of the world's deepest ocean abysses: the Mariana Trench and the Kermadec Trench. Their research was presented at an academic conference in Shanghai on June 8; it has not been published yet. 

The researchers discovered extremely high levels of chemical contaminants in amphipods (an order of crustaceans) captured between four and six miles down; these levels exceed those found in the most polluted rivers in China, Discover magazine reports

The chemicals found in the amphipods, PCBs and PBDEs, are known pollutants. PCBs (polychlorinated biphenyls) were once used as coolant fluid and in plasticizers but eventually labeled as possible human carcinogens, and since the 1970s their production has been banned in many countries, including the U.S. PBDEs (polybrominated diphenyl ethers) are man-made flame retardant chemicals that do not dissolve easily in water, and their degradation is aided by sunlight, which means the dark ocean floor might not the best place for them to be. 

These ocean trenches may be important carbon sinks with a role in regulating the Earth's climate. The more we understand what's happening deep inside them, the better we might understand the effect of these pollutants on both local ecosystems (which are largely a mystery) and the planet at large.  

[h/t Nature World News]