A team of British researchers discovered that man-made chemicals banned and subsequently dumped in the oceans in the 1970s still persist in the tissues of deep-sea creatures. The new findings have been published online in the journal Nature Ecology & Evolution on February 13th.
The researchers say that toxins of the past still reside within the bodies of amphipods, a type of crustaceans living in the deepest regions of the Pacific Ocean such as the Kermadec or Mariana trenches. To analyze the crustaceans, the scientists used deep-sea landers and scoured the bottom of the trenches that are situated 4,350 miles apart and measure 6.2 miles in depth.
By looking at the samples, the team of researchers concluded that the amphipods’ fatty tissue still contained high levels of Persistent Organic Pollutants, including polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs). During the 1970s, these compounds were used as flame retardants and electrical insulators but were later banned due to their high levels of toxicity.
Alan Jamieson at the Newcastle University and lead author of the study declared he was deeply troubled by his team’s recent findings. He stated that although it was previously thought the deep ocean is safe from human interaction, the levels of toxicity recorded in the amphipods’ fatty tissue resemble those found in Suruga Bay, one of the most polluted industrial areas in the northwest Pacific.
“It’s not a great legacy that we’re leaving behind”, said Alan Jamieson in his closing statement.
Over the course of four decades, starting with the 1940s when the toxic chemicals in question were first introduced to the market until they were banned in the 70s, the total global production was around 1.43 million tons. Scientists say that once the chemicals are released into the environment, they persist for decades as the pollutants are invulnerable to natural degradation.
The authors of the study believe large quantities of these toxic chemicals found their way to the bottom of the ocean through carrier dead animals sinking in the deep or contaminated plastic debris. Ultimately, the researchers said that because the pollutants accumulate through the food chain, the concentrations in the deep ocean waters exceed by far those recorded in surface waters.
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