Chemical pollutants are rife in the deep-sea food web, a new study has found, adding that many contaminants were showing up in marine organisms like octopods and squids.
The study was carried out by Michael Vecchione of NOAA Fisheries' National Systematics Laboratory and colleagues Michael Unger, Ellen Harvey and George Vadas at the Virginia Institute of Marine Science of The College of William and Mary.
They report finding a variety of chemical contaminants in nine species of cephalopods, a class of organisms that includes octopods, squids, cuttlefishes and nautiluses.
Cephalopods are important to the diet of cetaceans, a class of marine mammals which includes whales, dolphins and porpoises.
They are the primary food for 28 species of odontocetes, the sub-order of cetaceans that have teeth and include beaked, sperm, killer and beluga whales and narwhals as well as dolphins and porpoises.
Recent studies have reported the accumulation of persistent organic pollutants (POPs) in the blubber and tissues of whales and other predatory marine mammals as well as in some deep-sea fish. Other investigators had speculated that the pollutants in marine mammals had resulted from feeding on contaminated squids.
However, almost no information existed prior to this study about POPs in deep-sea cephalopods.
"It was surprising to find measurable and sometimes high amounts of toxic pollutants in such a deep and remote environment," said Vecchione.
Vecchione and colleagues wanted to see if whales had a unique capacity to accumulate pollutants or if they were simply one of the top predators in a contaminated deep-sea food web.
The researchers collected nine species of cephalopods from depths between 1,000 and 2,000 meters (about 3,300 to 6,600 feet) in 2003 in the western North Atlantic Ocean using a large mid-water trawl.
Among the chemicals detected were tributyltin (TBT), polychlorinated biphenyls (PCBs), brominated diphenyl ethers (BDEs), and dichlorodiphenyl-trichloroethane (DDT). They are known as persistent organic pollutants because they don't degrade and persist in the environment for a very long time.
Other chemical contaminants found in the specimens include polycyclic aromatic hydrocarbons (PAHs), found in all the samples, diphenyl ether (DPE), polychlorinated biphenyls (PCBs), and brominated diphenyl ethers (BDEs).
The researchers also detected DDT, a pesticide banned in the US in the 1970s, but still used on a limited basis in some parts of the world to control diseases like malaria.
According to Vecchione, "The fact that we detected a variety of pollutants in specimens collected from more than 3,000 feet deep is evidence that human-produced chemicals are reaching remote areas of the open ocean, accumulating in prey species, and therefore available to higher levels of marine life."
"Contamination of the deep-sea food web is happening, and it is a real concern," he added.